`narwhals.Series`

Narwhals Series, backed by a native series.

Warning

This class is not meant to be instantiated directly - instead:

If the native object is a series from one of the supported backend (e.g. pandas.Series, polars.Series, pyarrow.ChunkedArray), you can use narwhals.from_native:
```
narwhals.from_native(native_series, allow_series=True)
narwhals.from_native(native_series, series_only=True)
```

If the object is a generic sequence (e.g. a list or a tuple of values), you can create a series via narwhals.new_series:

narwhals.new_series(
    name=name,
    values=values,
    native_namespace=narwhals.get_native_namespace(another_object),
)

`dtype: DType` `property`

Get the data type of the Series.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> nw.dtypes.DType:
...     s = nw.from_native(s_native, series_only=True)
...     return s.dtype

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
Int64
>>> my_library_agnostic_function(s_pl)
Int64

`implementation: Implementation` `property`

Return implementation of native Series.

This can be useful when you need to some special-casing for some libraries for features outside of Narwhals' scope - for example, when dealing with pandas' Period Dtype.

Returns:

Type	Description
`Implementation`	Implementation.

Examples:

>>> import narwhals as nw
>>> import pandas as pd
>>> s_native = pd.Series([1, 2, 3])
>>> s = nw.from_native(s_native, series_only=True)
>>> s.implementation
<Implementation.PANDAS: 1>
>>> s.implementation.is_pandas()
True
>>> s.implementation.is_pandas_like()
True
>>> s.implementation.is_polars()
False

`name: str` `property`

Get the name of the Series.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s, name="foo")
>>> s_pl = pl.Series("foo", s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries) -> str:
...     s = nw.from_native(s_native, series_only=True)
...     return s.name

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
'foo'
>>> my_library_agnostic_function(s_pl)
'foo'

`shape: tuple[int]` `property`

Get the shape of the Series.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries) -> tuple[int]:
...     s = nw.from_native(s_native, series_only=True)
...     return s.shape

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
(3,)
>>> my_library_agnostic_function(s_pl)
(3,)

`__arrow_c_stream__(requested_schema=None)`

Export a Series via the Arrow PyCapsule Interface.

Narwhals doesn't implement anything itself here:

if the underlying series implements the interface, it'll return that
else, it'll call to_arrow and then defer to PyArrow's implementation

See PyCapsule Interface for more.

`getitem(idx)`

Retrieve elements from the object using integer indexing or slicing.

Parameters:

Name	Type	Description	Default
`idx`	`int \| slice \| Sequence[int]`	The index, slice, or sequence of indices to retrieve. If `idx` is an integer, a single element is returned. If `idx` is a slice or a sequence of integers, a subset of the Series is returned.	required

Returns:

Type	Description
`Any \| Self`	A single element if `idx` is an integer, else a subset of the Series.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> from typing import Any
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)
>>> s_pa = pa.chunked_array([s])

We define a library agnostic function:

>>> def agnostic_get_first_item(s_native: IntoSeriesT) -> Any:
...     s = nw.from_native(s_native, series_only=True)
...     return s[0]

We can then pass either pandas, Polars, or any supported library:

>>> agnostic_get_first_item(s_pd)
np.int64(1)
>>> agnostic_get_first_item(s_pl)
1
>>> agnostic_get_first_item(s_pa)
1

We can also make a function to slice the Series:

>>> def agnostic_slice(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s[:2].to_native()

>>> agnostic_slice(s_pd)
0    1
1    2
dtype: int64
>>> agnostic_slice(s_pl)
shape: (2,)
Series: '' [i64]
[
    1
    2
]
>>> agnostic_slice(s_pa)
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    1,
    2
  ]
]

`iter()`

`abs()`

Calculate the absolute value of each element.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s = [2, -4, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a dataframe-agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.abs().to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    2
1    4
2    3
dtype: int64
>>> my_library_agnostic_function(s_pl)
shape: (3,)
Series: '' [i64]
[
   2
   4
   3
]

`alias(name)`

Rename the Series.

Notes

This method is very cheap, but does not guarantee that data will be copied. For example:

s1: nw.Series
s2 = s1.alias("foo")
arr = s2.to_numpy()
arr[0] = 999

may (depending on the backend, and on the version) result in s1's data being modified. We recommend:

- if you need to alias an object and don't need the original
  one around any more, just use `alias` without worrying about it.
- if you were expecting `alias` to copy data, then explicily call
  `.clone` before calling `alias`.

Parameters:

Name	Type	Description	Default
`name`	`str`	The new name.	required

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s, name="foo")
>>> s_pl = pl.Series("foo", s)
>>> s_pa = pa.chunked_array([s])

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.alias("bar").to_native()

We can then pass any supported library such as pandas, Polars, or PyArrow:

>>> my_library_agnostic_function(s_pd)
0    1
1    2
2    3
Name: bar, dtype: int64
>>> my_library_agnostic_function(s_pl)
shape: (3,)
Series: 'bar' [i64]
[
   1
   2
   3
]
>>> my_library_agnostic_function(s_pa)
<pyarrow.lib.ChunkedArray object at 0x...>
[
  [
    1,
    2,
    3
  ]
]

`all()`

Return whether all values in the Series are True.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [True, False, True]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.all()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
np.False_
>>> my_library_agnostic_function(s_pl)
False

`any()`

Return whether any of the values in the Series are True.

Notes

Only works on Series of data type Boolean.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [False, True, False]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.any()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
np.True_
>>> my_library_agnostic_function(s_pl)
True

`arg_max()`

Returns the index of the maximum value.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)
>>> s_pa = pa.chunked_array([s])

We define a library agnostic function:

>>> def agnostic_arg_max(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.arg_max()

We can then pass either any supported library such as pandas, Polars, or PyArrow:

>>> agnostic_arg_max(s_pd)
np.int64(2)
>>> agnostic_arg_max(s_pl)
2
>>> agnostic_arg_max(s_pa)
2

`arg_min()`

Returns the index of the minimum value.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)
>>> s_pa = pa.chunked_array([s])

We define a library agnostic function:

>>> def agnostic_arg_min(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.arg_min()

We can then pass either any supported library such as pandas, Polars, or PyArrow:

>>> agnostic_arg_min(s_pd)
np.int64(0)
>>> agnostic_arg_min(s_pl)
0
>>> agnostic_arg_min(s_pa)
0

`arg_true()`

Find elements where boolean Series is True.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> data = [1, None, None, 2]
>>> s_pd = pd.Series(data, name="a")
>>> s_pl = pl.Series("a", data)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.is_null().arg_true().to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
1    1
2    2
Name: a, dtype: int64
>>> my_library_agnostic_function(s_pl)
shape: (2,)
Series: 'a' [u32]
[
   1
   2
]

`cast(dtype)`

Cast between data types.

Parameters:

Name	Type	Description	Default
`dtype`	`DType \| type[DType]`	Data type that the object will be cast into.	required

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s = [True, False, True]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a dataframe-agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.cast(nw.Int64).to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    1
1    0
2    1
dtype: int64
>>> my_library_agnostic_function(s_pl)
shape: (3,)
Series: '' [i64]
[
   1
   0
   1
]

`clip(lower_bound=None, upper_bound=None)`

Clip values in the Series.

Parameters:

Name	Type	Description	Default
`lower_bound`	`Any \| None`	Lower bound value.	`None`
`upper_bound`	`Any \| None`	Upper bound value.	`None`

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>>
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def clip_lower(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.clip(2).to_native()

We can then pass either pandas or Polars to clip_lower:

>>> clip_lower(s_pd)
0    2
1    2
2    3
dtype: int64
>>> clip_lower(s_pl)
shape: (3,)
Series: '' [i64]
[
   2
   2
   3
]

We define another library agnostic function:

>>> def clip_upper(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.clip(upper_bound=2).to_native()

We can then pass either pandas or Polars to clip_upper:

>>> clip_upper(s_pd)
0    1
1    2
2    2
dtype: int64
>>> clip_upper(s_pl)
shape: (3,)
Series: '' [i64]
[
   1
   2
   2
]

We can have both at the same time

>>> s = [-1, 1, -3, 3, -5, 5]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.clip(-1, 3).to_native()

We can pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0   -1
1    1
2   -1
3    3
4   -1
5    3
dtype: int64
>>> my_library_agnostic_function(s_pl)
shape: (6,)
Series: '' [i64]
[
   -1
    1
   -1
    3
   -1
    3
]

`count()`

Returns the number of non-null elements in the Series.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.count()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
np.int64(3)
>>> my_library_agnostic_function(s_pl)
3

`cum_count(*, reverse=False)`

Return the cumulative count of the non-null values in the series.

Parameters:

Name	Type	Description	Default
`reverse`	`bool`	reverse the operation	`False`

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> data = ["x", "k", None, "d"]

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.cum_count(reverse=True).to_native()

We can then pass any supported library such as Pandas, Polars, or PyArrow to func:

>>> my_library_agnostic_function(pd.Series(data))
0    3
1    2
2    1
3    1
dtype: int64
>>> my_library_agnostic_function(pl.Series(data))
shape: (4,)
Series: '' [u32]
[
    3
    2
    1
    1
]
>>> my_library_agnostic_function(pa.chunked_array([data]))
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    3,
    2,
    1,
    1
  ]
]

`cum_max(*, reverse=False)`

Return the cumulative max of the non-null values in the series.

Parameters:

Name	Type	Description	Default
`reverse`	`bool`	reverse the operation	`False`

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> data = [1, 3, None, 2]

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.cum_max().to_native()

We can then pass any supported library such as Pandas, Polars, or PyArrow to func:

>>> my_library_agnostic_function(pd.Series(data))
0    1.0
1    3.0
2    NaN
3    3.0
dtype: float64
>>> my_library_agnostic_function(pl.Series(data))
shape: (4,)
Series: '' [i64]
[
   1
   3
   null
   3
]
>>> my_library_agnostic_function(pa.chunked_array([data]))
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    1,
    3,
    null,
    3
  ]
]

`cum_min(*, reverse=False)`

Return the cumulative min of the non-null values in the series.

Parameters:

Name	Type	Description	Default
`reverse`	`bool`	reverse the operation	`False`

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> data = [3, 1, None, 2]

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.cum_min().to_native()

We can then pass any supported library such as Pandas, Polars, or PyArrow to func:

>>> my_library_agnostic_function(pd.Series(data))
0    3.0
1    1.0
2    NaN
3    1.0
dtype: float64
>>> my_library_agnostic_function(pl.Series(data))
shape: (4,)
Series: '' [i64]
[
   3
   1
   null
   1
]
>>> my_library_agnostic_function(pa.chunked_array([data]))
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    3,
    1,
    null,
    1
  ]
]

`cum_prod(*, reverse=False)`

Return the cumulative product of the non-null values in the series.

Parameters:

Name	Type	Description	Default
`reverse`	`bool`	reverse the operation	`False`

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> data = [1, 3, None, 2]

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.cum_prod().to_native()

We can then pass any supported library such as Pandas, Polars, or PyArrow to func:

>>> my_library_agnostic_function(pd.Series(data))
0    1.0
1    3.0
2    NaN
3    6.0
dtype: float64
>>> my_library_agnostic_function(pl.Series(data))
shape: (4,)
Series: '' [i64]
[
   1
   3
   null
   6
]
>>> my_library_agnostic_function(pa.chunked_array([data]))
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    1,
    3,
    null,
    6
  ]
]

`cum_sum(*, reverse=False)`

Calculate the cumulative sum.

Parameters:

Name	Type	Description	Default
`reverse`	`bool`	reverse the operation	`False`

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s = [2, 4, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a dataframe-agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.cum_sum().to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    2
1    6
2    9
dtype: int64
>>> my_library_agnostic_function(s_pl)
shape: (3,)
Series: '' [i64]
[
   2
   6
   9
]

`diff()`

Calculate the difference with the previous element, for each element.

Notes

pandas may change the dtype here, for example when introducing missing values in an integer column. To ensure, that the dtype doesn't change, you may want to use fill_null and cast. For example, to calculate the diff and fill missing values with 0 in a Int64 column, you could do:

s.diff().fill_null(0).cast(nw.Int64)

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s = [2, 4, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a dataframe-agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.diff().to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    NaN
1    2.0
2   -1.0
dtype: float64
>>> my_library_agnostic_function(s_pl)
shape: (3,)
Series: '' [i64]
[
   null
   2
   -1
]

`drop_nulls()`

Drop null values.

Notes

pandas handles null values differently from Polars and PyArrow. See null_handling for reference.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s_pd = pd.Series([2, 4, None, 3, 5])
>>> s_pl = pl.Series([2, 4, None, 3, 5])
>>> s_pa = pa.chunked_array([[2, 4, None, 3, 5]])

Let's define a dataframe-agnostic function:

>>> def agnostic_drop_nulls(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.drop_nulls().to_native()

We can then pass any supported library such as Pandas, Polars, or PyArrow to agnostic_drop_nulls:

>>> agnostic_drop_nulls(s_pd)
0    2.0
1    4.0
3    3.0
4    5.0
dtype: float64
>>> agnostic_drop_nulls(s_pl)
shape: (4,)
Series: '' [i64]
[
    2
    4
    3
    5
]
>>> agnostic_drop_nulls(s_pa)
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    2,
    4,
    3,
    5
  ]
]

`ewm_mean(*, com=None, span=None, half_life=None, alpha=None, adjust=True, min_periods=1, ignore_nulls=False)`

Compute exponentially-weighted moving average.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

Parameters:

Name	Type	Description	Default
`com`	`float \| None`	Specify decay in terms of center of mass, $\gamma$, with $\alpha = \frac{1}{1+\gamma}\forall\gamma\geq0$	`None`
`span`	`float \| None`	Specify decay in terms of span, $\theta$, with $\alpha = \frac{2}{\theta + 1} \forall \theta \geq 1$	`None`
`half_life`	`float \| None`	Specify decay in terms of half-life, $\tau$, with $\alpha = 1 - \exp \left\{ \frac{ -\ln(2) }{ \tau } \right\} \forall \tau > 0$	`None`
`alpha`	`float \| None`	Specify smoothing factor alpha directly, $0 < \alpha \leq 1$.	`None`
`adjust`	`bool`	Divide by decaying adjustment factor in beginning periods to account for imbalance in relative weightings When `adjust=True` (the default) the EW function is calculated using weights $w_i = (1 - \alpha)^i$ When `adjust=False` the EW function is calculated recursively by $$ y_0=x_0 $$ $$ y_t = (1 - \alpha)y_{t - 1} + \alpha x_t $$	`True`
`min_periods`	`int`	Minimum number of observations in window required to have a value (otherwise result is null).	`1`
`ignore_nulls`	`bool`	Ignore missing values when calculating weights. When `ignore_nulls=False` (default), weights are based on absolute positions. For example, the weights of $x_0$ and $x_2$ used in calculating the final weighted average of $[x_0, None, x_2]$ are $(1-\alpha)^2$ and $1$ if `adjust=True`, and $(1-\alpha)^2$ and $\alpha$ if `adjust=False`. When `ignore_nulls=True`, weights are based on relative positions. For example, the weights of $x_0$ and $x_2$ used in calculating the final weighted average of $[x_0, None, x_2]$ are $1-\alpha$ and $1$ if `adjust=True`, and $1-\alpha$ and $\alpha$ if `adjust=False`.	`False`

Returns:

Type	Description
`Self`	Series

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> data = [1, 2, 3]
>>> s_pd = pd.Series(name="a", data=data)
>>> s_pl = pl.Series(name="a", values=data)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.ewm_mean(com=1, ignore_nulls=False).to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    1.000000
1    1.666667
2    2.428571
Name: a, dtype: float64

>>> my_library_agnostic_function(s_pl)
shape: (3,)
Series: 'a' [f64]
[
   1.0
   1.666667
   2.428571
]

`fill_null(value=None, strategy=None, limit=None)`

Fill null values using the specified value.

Parameters:

Name	Type	Description	Default
`value`	`Any \| None`	Value used to fill null values.	`None`
`strategy`	`Literal['forward', 'backward'] \| None`	Strategy used to fill null values.	`None`
`limit`	`int \| None`	Number of consecutive null values to fill when using the 'forward' or 'backward' strategy.	`None`

Notes

pandas handles null values differently from Polars and PyArrow. See null_handling for reference.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s = [1, 2, None]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)
>>> s_pa = pa.chunked_array([s])

Let's define a dataframe-agnostic function:

>>> def agnostic_fill_null(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.fill_null(5).to_native()

We can then pass any supported library such as pandas, Polars, or PyArrow to agnostic_fill_null:

>>> agnostic_fill_null(s_pd)
0    1.0
1    2.0
2    5.0
dtype: float64
>>> agnostic_fill_null(s_pl)
shape: (3,)
Series: '' [i64]
[
   1
   2
   5
]
>>> agnostic_fill_null(s_pa)
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    1,
    2,
    5
  ]
]

Using a strategy:

>>> def agnostic_fill_null_with_strategy(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.fill_null(strategy="forward", limit=1).to_native()

>>> agnostic_fill_null_with_strategy(s_pd)
0    1.0
1    2.0
2    2.0
dtype: float64
>>> agnostic_fill_null_with_strategy(s_pl)
shape: (3,)
Series: '' [i64]
[
   1
   2
   2
]
>>> agnostic_fill_null_with_strategy(s_pa)
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    1,
    2,
    2
  ]
]

`filter(other)`

Filter elements in the Series based on a condition.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s = [4, 10, 15, 34, 50]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.filter(s > 10).to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
2    15
3    34
4    50
dtype: int64
>>> my_library_agnostic_function(s_pl)
shape: (3,)
Series: '' [i64]
[
   15
   34
   50
]

`gather_every(n, offset=0)`

Take every nth value in the Series and return as new Series.

Parameters:

Name	Type	Description	Default
`n`	`int`	Gather every n-th row.	required
`offset`	`int`	Starting index.	`0`

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> data = [1, 2, 3, 4]
>>> s_pd = pd.Series(name="a", data=data)
>>> s_pl = pl.Series(name="a", values=data)

Let's define a dataframe-agnostic function in which gather every 2 rows, starting from a offset of 1:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.gather_every(n=2, offset=1).to_native()

>>> my_library_agnostic_function(s_pd)
1    2
3    4
Name: a, dtype: int64

>>> my_library_agnostic_function(s_pl)
shape: (2,)
Series: 'a' [i64]
[
   2
   4
]

`head(n=10)`

Get the first n rows.

Parameters:

Name	Type	Description	Default
`n`	`int`	Number of rows to return.	`10`

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> data = list(range(10))
>>> s_pd = pd.Series(data)
>>> s_pl = pl.Series(data)

Let's define a dataframe-agnostic function that returns the first 3 rows:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.head(3).to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    0
1    1
2    2
dtype: int64

>>> my_library_agnostic_function(s_pl)
shape: (3,)
Series: '' [i64]
[
   0
   1
   2
]

`is_between(lower_bound, upper_bound, closed='both')`

Get a boolean mask of the values that are between the given lower/upper bounds.

Parameters:

Name	Type	Description	Default
`lower_bound`	`Any`	Lower bound value.	required
`upper_bound`	`Any`	Upper bound value.	required
`closed`	`str`	Define which sides of the interval are closed (inclusive).	`'both'`

Notes

If the value of the lower_bound is greater than that of the upper_bound, then the values will be False, as no value can satisfy the condition.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s_pd = pd.Series([1, 2, 3, 4, 5])
>>> s_pl = pl.Series([1, 2, 3, 4, 5])

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.is_between(2, 4, "right").to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    False
1    False
2     True
3     True
4    False
dtype: bool
>>> my_library_agnostic_function(s_pl)
shape: (5,)
Series: '' [bool]
[
   false
   false
   true
   true
   false
]

`is_duplicated()`

Get a mask of all duplicated rows in the Series.

Returns:

Type	Description
`Self`	A new Series.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> s_pd = pd.Series([1, 2, 3, 1])
>>> s_pl = pl.Series([1, 2, 3, 1])

Let's define a dataframe-agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.is_duplicated().to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0     True
1    False
2    False
3     True
dtype: bool
>>> my_library_agnostic_function(s_pl)
shape: (4,)
Series: '' [bool]
[
    true
    false
    false
    true
]

`is_empty()`

Check if the series is empty.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> import pandas as pd
>>> import polars as pl

Let's define a dataframe-agnostic function that filters rows in which "foo" values are greater than 10, and then checks if the result is empty or not:

>>> def my_library_agnostic_function(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.filter(s > 10).is_empty()

We can then pass either pandas or Polars to func:

>>> s_pd = pd.Series([1, 2, 3])
>>> s_pl = pl.Series([1, 2, 3])
>>> my_library_agnostic_function(s_pd), my_library_agnostic_function(s_pl)
(True, True)

>>> s_pd = pd.Series([100, 2, 3])
>>> s_pl = pl.Series([100, 2, 3])
>>> my_library_agnostic_function(s_pd), my_library_agnostic_function(s_pl)
(False, False)

`is_finite()`

Returns a boolean Series indicating which values are finite.

Warning

Different backend handle null values differently. is_finite will return False for NaN and Null's in the Dask and pandas non-nullable backend, while for Polars, PyArrow and pandas nullable backends null values are kept as such.

Returns:

Type	Description
`Self`	Expression of `Boolean` data type.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> data = [float("nan"), float("inf"), 2.0, None]

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.is_finite().to_native()

We can then pass any supported library such as Pandas, Polars, or PyArrow to func:

>>> my_library_agnostic_function(pd.Series(data))
0    False
1    False
2     True
3    False
dtype: bool

>>> my_library_agnostic_function(
...     pl.Series(data)
... )
shape: (4,)
Series: '' [bool]
[
   false
   false
   true
   null
]

>>> my_library_agnostic_function(pa.chunked_array([data]))
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    false,
    false,
    true,
    null
  ]
]

`is_first_distinct()`

Return a boolean mask indicating the first occurrence of each distinct value.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> s_pd = pd.Series([1, 1, 2, 3, 2])
>>> s_pl = pl.Series([1, 1, 2, 3, 2])

Let's define a dataframe-agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.is_first_distinct().to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0     True
1    False
2     True
3     True
4    False
dtype: bool

>>> my_library_agnostic_function(s_pl)
shape: (5,)
Series: '' [bool]
[
    true
    false
    true
    true
    false
]

`is_in(other)`

Check if the elements of this Series are in the other sequence.

Parameters:

Name	Type	Description	Default
`other`	`Any`	Sequence of primitive type.	required

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s_pd = pd.Series([1, 2, 3])
>>> s_pl = pl.Series([1, 2, 3])

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.is_in([3, 2, 8]).to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    False
1     True
2     True
dtype: bool
>>> my_library_agnostic_function(s_pl)
shape: (3,)
Series: '' [bool]
[
   false
   true
   true
]

`is_last_distinct()`

Return a boolean mask indicating the last occurrence of each distinct value.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> s_pd = pd.Series([1, 1, 2, 3, 2])
>>> s_pl = pl.Series([1, 1, 2, 3, 2])

Let's define a dataframe-agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.is_last_distinct().to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    False
1     True
2    False
3     True
4     True
dtype: bool

>>> my_library_agnostic_function(s_pl)
shape: (5,)
Series: '' [bool]
[
    false
    true
    false
    true
    true
]

`is_null()`

Returns a boolean Series indicating which values are null.

Notes

pandas handles null values differently from Polars and PyArrow. See null_handling for reference.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> import pyarrow as pa
>>> from narwhals.typing import IntoSeriesT
>>> s = [1, 2, None]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)
>>> s_pa = pa.chunked_array([s])

Let's define a dataframe-agnostic function:

>>> def agnostic_is_null(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.is_null().to_native()

We can then pass any supported library such as Pandas, Polars, or PyArrow to agnostic_is_null:

>>> agnostic_is_null(s_pd)
0    False
1    False
2     True
dtype: bool
>>> agnostic_is_null(s_pl)
shape: (3,)
Series: '' [bool]
[
   false
   false
   true
]
>>> agnostic_is_null(s_pa)
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    false,
    false,
    true
  ]
]

`is_sorted(*, descending=False)`

Check if the Series is sorted.

Parameters:

Name	Type	Description	Default
`descending`	`bool`	Check if the Series is sorted in descending order.	`False`

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> import pandas as pd
>>> import polars as pl
>>> unsorted_data = [1, 3, 2]
>>> sorted_data = [3, 2, 1]

Let's define a dataframe-agnostic function:

>>> def my_library_agnostic_function(
...     s_native: IntoSeries, descending: bool = False
... ):
...     s = nw.from_native(s_native, series_only=True)
...     return s.is_sorted(descending=descending)

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(pl.Series(unsorted_data))
False
>>> my_library_agnostic_function(pl.Series(sorted_data), descending=True)
True
>>> my_library_agnostic_function(pd.Series(unsorted_data))
False
>>> my_library_agnostic_function(pd.Series(sorted_data), descending=True)
True

`is_unique()`

Get a mask of all unique rows in the Series.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> s_pd = pd.Series([1, 2, 3, 1])
>>> s_pl = pl.Series([1, 2, 3, 1])

Let's define a dataframe-agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.is_unique().to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    False
1     True
2     True
3    False
dtype: bool

>>> my_library_agnostic_function(s_pl)
shape: (4,)
Series: '' [bool]
[
    false
     true
     true
    false
]

`item(index=None)`

Return the Series as a scalar, or return the element at the given index.

If no index is provided, this is equivalent to s[0], with a check that the shape is (1,). With an index, this is equivalent to s[index].

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> import pandas as pd
>>> import polars as pl

Let's define a dataframe-agnostic function that returns item at given index

>>> def my_library_agnostic_function(s_native: IntoSeries, index=None):
...     s = nw.from_native(s_native, series_only=True)
...     return s.item(index)

We can then pass either pandas or Polars to func:

>>> (
...     my_library_agnostic_function(pl.Series("a", [1]), None),
...     my_library_agnostic_function(pd.Series([1]), None),
... )
(1, np.int64(1))

>>> (
...     my_library_agnostic_function(pl.Series("a", [9, 8, 7]), -1),
...     my_library_agnostic_function(pl.Series([9, 8, 7]), -2),
... )
(7, 8)

`len()`

Return the number of elements in the Series.

Null values count towards the total.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> import pandas as pd
>>> import polars as pl
>>> data = [1, 2, None]
>>> s_pd = pd.Series(data)
>>> s_pl = pl.Series(data)

Let's define a dataframe-agnostic function that computes the len of the series:

>>> def my_library_agnostic_function(s_native: IntoSeries) -> int:
...     s = nw.from_native(s_native, series_only=True)
...     return s.len()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
3
>>> my_library_agnostic_function(s_pl)
3

`max()`

Get the maximum value in this Series.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.max()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
np.int64(3)
>>> my_library_agnostic_function(s_pl)
3

`mean()`

Reduce this Series to the mean value.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.mean()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
np.float64(2.0)
>>> my_library_agnostic_function(s_pl)
2.0

`median()`

Reduce this Series to the median value.

Notes

Results might slightly differ across backends due to differences in the underlying algorithms used to compute the median.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [5, 3, 8]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)
>>> s_pa = pa.chunked_array([s])

Let's define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.median()

We can then pass any supported library such as pandas, Polars, or PyArrow to func:

>>> my_library_agnostic_function(s_pd)
np.float64(5.0)
>>> my_library_agnostic_function(s_pl)
5.0
>>> my_library_agnostic_function(s_pa)
5.0

`min()`

Get the minimal value in this Series.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.min()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
np.int64(1)
>>> my_library_agnostic_function(s_pl)
1

`mode()`

Compute the most occurring value(s).

Can return multiple values.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT

>>> data = [1, 1, 2, 2, 3]
>>> s_pd = pd.Series(name="a", data=data)
>>> s_pl = pl.Series(name="a", values=data)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.mode().sort().to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    1
1    2
Name: a, dtype: int64

>>> my_library_agnostic_function(s_pl)
shape: (2,)
Series: 'a' [i64]
[
   1
   2
]

`n_unique()`

Count the number of unique values.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [1, 2, 2, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.n_unique()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
3
>>> my_library_agnostic_function(s_pl)
3

`null_count()`

Create a new Series that shows the null counts per column.

Notes

pandas handles null values differently from Polars and PyArrow. See null_handling for reference.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> s = [1, None, None]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)
>>> s_pa = pa.chunked_array([s])

Let's define a dataframe-agnostic function that returns the null count of the series:

>>> def agnostic_null_count(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.null_count()

We can then pass any supported library such as pandas, Polars, or PyArrow to agnostic_null_count:

>>> agnostic_null_count(s_pd)
np.int64(2)
>>> agnostic_null_count(s_pl)
2
>>> agnostic_null_count(s_pa)
2

`pipe(function, *args, **kwargs)`

Pipe function call.

Examples:

>>> import polars as pl
>>> import pandas as pd
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s_pd = pd.Series([1, 2, 3, 4])
>>> s_pl = pl.Series([1, 2, 3, 4])

Lets define a function to pipe into

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.pipe(lambda x: x + 2).to_native()

Now apply it to the series

>>> my_library_agnostic_function(s_pd)
0    3
1    4
2    5
3    6
dtype: int64
>>> my_library_agnostic_function(s_pl)
shape: (4,)
Series: '' [i64]
[
   3
   4
   5
   6
]

`quantile(quantile, interpolation)`

Get quantile value of the series.

Note

pandas and Polars may have implementation differences for a given interpolation method.

Parameters:

Name	Type	Description	Default
`quantile`	`float`	Quantile between 0.0 and 1.0.	required
`interpolation`	`Literal['nearest', 'higher', 'lower', 'midpoint', 'linear']`	Interpolation method.	required

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> import pandas as pd
>>> import polars as pl
>>> data = list(range(50))
>>> s_pd = pd.Series(data)
>>> s_pl = pl.Series(data)

Let's define a dataframe-agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return [
...         s.quantile(quantile=q, interpolation="nearest")
...         for q in (0.1, 0.25, 0.5, 0.75, 0.9)
...     ]

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
[np.int64(5), np.int64(12), np.int64(24), np.int64(37), np.int64(44)]

>>> my_library_agnostic_function(s_pl)
[5.0, 12.0, 25.0, 37.0, 44.0]

`rename(name)`

Rename the Series.

Alias for Series.alias().

Notes

This method is very cheap, but does not guarantee that data will be copied. For example:

s1: nw.Series
s2 = s1.rename("foo")
arr = s2.to_numpy()
arr[0] = 999

may (depending on the backend, and on the version) result in s1's data being modified. We recommend:

- if you need to rename an object and don't need the original
  one around any more, just use `rename` without worrying about it.
- if you were expecting `rename` to copy data, then explicily call
  `.clone` before calling `rename`.

Parameters:

Name	Type	Description	Default
`name`	`str`	The new name.	required

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s, name="foo")
>>> s_pl = pl.Series("foo", s)
>>> s_pa = pa.chunked_array([s])

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.rename("bar").to_native()

We can then pass any supported library such as pandas, Polars, or PyArrow:

>>> my_library_agnostic_function(s_pd)
0    1
1    2
2    3
Name: bar, dtype: int64
>>> my_library_agnostic_function(s_pl)
shape: (3,)
Series: 'bar' [i64]
[
   1
   2
   3
]
>>> my_library_agnostic_function(s_pa)
<pyarrow.lib.ChunkedArray object at 0x...>
[
  [
    1,
    2,
    3
  ]
]

`replace_strict(old, new=None, *, return_dtype=None)`

Replace all values by different values.

This function must replace all non-null input values (else it raises an error).

Parameters:

Name	Type	Description	Default
`old`	`Sequence[Any] \| Mapping[Any, Any]`	Sequence of values to replace. It also accepts a mapping of values to their replacement as syntactic sugar for `replace_all(old=list(mapping.keys()), new=list(mapping.values()))`.	required
`new`	`Sequence[Any] \| None`	Sequence of values to replace by. Length must match the length of `old`.	`None`
`return_dtype`	`DType \| type[DType] \| None`	The data type of the resulting expression. If set to `None` (default), the data type is determined automatically based on the other inputs.	`None`

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> df_pd = pd.DataFrame({"a": [3, 0, 1, 2]})
>>> df_pl = pl.DataFrame({"a": [3, 0, 1, 2]})
>>> df_pa = pa.table({"a": [3, 0, 1, 2]})

Let's define dataframe-agnostic functions:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.replace_strict(
...         [0, 1, 2, 3], ["zero", "one", "two", "three"], return_dtype=nw.String
...     ).to_native()

We can then pass any supported library such as Pandas, Polars, or PyArrow to func:

>>> my_library_agnostic_function(df_pd["a"])
0    three
1     zero
2      one
3      two
Name: a, dtype: object
>>> my_library_agnostic_function(df_pl["a"])
shape: (4,)
Series: 'a' [str]
[
    "three"
    "zero"
    "one"
    "two"
]
>>> my_library_agnostic_function(df_pa["a"])
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    "three",
    "zero",
    "one",
    "two"
  ]
]

`rolling_mean(window_size, *, min_periods=None, center=False)`

Apply a rolling mean (moving mean) over the values.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

A window of length window_size will traverse the values. The resulting values will be aggregated to their mean.

The window at a given row will include the row itself and the window_size - 1 elements before it.

Parameters:

Name	Type	Description	Default
`window_size`	`int`	The length of the window in number of elements. It must be a strictly positive integer.	required
`min_periods`	`int \| None`	The number of values in the window that should be non-null before computing a result. If set to `None` (default), it will be set equal to `window_size`. If provided, it must be a strictly positive integer, and less than or equal to `window_size`	`None`
`center`	`bool`	Set the labels at the center of the window.	`False`

Returns:

Type	Description
`Self`	A new series.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> data = [1.0, 2.0, 3.0, 4.0]
>>> s_pd = pd.Series(data)
>>> s_pl = pl.Series(data)
>>> s_pa = pa.chunked_array([data])

We define a library agnostic function:

>>> def agnostic_rolling_mean(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.rolling_mean(window_size=2).to_native()

We can then pass any supported library such as Pandas, Polars, or PyArrow to func:

>>> agnostic_rolling_mean(s_pd)
0    NaN
1    1.5
2    2.5
3    3.5
dtype: float64

>>> agnostic_rolling_mean(s_pl)
shape: (4,)
Series: '' [f64]
[
   null
   1.5
   2.5
   3.5
]

>>> agnostic_rolling_mean(s_pa)
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    null,
    1.5,
    2.5,
    3.5
  ]
]

`rolling_std(window_size, *, min_periods=None, center=False, ddof=1)`

Apply a rolling standard deviation (moving standard deviation) over the values.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

A window of length window_size will traverse the values. The resulting values will be aggregated to their standard deviation.

The window at a given row will include the row itself and the window_size - 1 elements before it.

Parameters:

Name	Type	Description	Default
`window_size`	`int`	The length of the window in number of elements. It must be a strictly positive integer.	required
`min_periods`	`int \| None`	The number of values in the window that should be non-null before computing a result. If set to `None` (default), it will be set equal to `window_size`. If provided, it must be a strictly positive integer, and less than or equal to `window_size`.	`None`
`center`	`bool`	Set the labels at the center of the window.	`False`
`ddof`	`int`	Delta Degrees of Freedom; the divisor for a length N window is N - ddof.	`1`

Returns:

Type	Description
`Self`	A new series.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> data = [1.0, 3.0, 1.0, 4.0]
>>> s_pd = pd.Series(data)
>>> s_pl = pl.Series(data)
>>> s_pa = pa.chunked_array([data])

We define a library agnostic function:

>>> def agnostic_rolling_std(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.rolling_std(window_size=2, min_periods=1).to_native()

We can then pass any supported library such as Pandas, Polars, or PyArrow to func:

>>> agnostic_rolling_std(s_pd)
0         NaN
1    1.414214
2    1.414214
3    2.121320
dtype: float64

>>> agnostic_rolling_std(s_pl)
shape: (4,)
Series: '' [f64]
[
   null
   1.414214
   1.414214
   2.12132
]

>>> agnostic_rolling_std(s_pa)
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    nan,
    1.4142135623730951,
    1.4142135623730951,
    2.1213203435596424
  ]
]

`rolling_sum(window_size, *, min_periods=None, center=False)`

Apply a rolling sum (moving sum) over the values.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

A window of length window_size will traverse the values. The resulting values will be aggregated to their sum.

The window at a given row will include the row itself and the window_size - 1 elements before it.

Parameters:

Name	Type	Description	Default
`window_size`	`int`	The length of the window in number of elements. It must be a strictly positive integer.	required
`min_periods`	`int \| None`	The number of values in the window that should be non-null before computing a result. If set to `None` (default), it will be set equal to `window_size`. If provided, it must be a strictly positive integer, and less than or equal to `window_size`	`None`
`center`	`bool`	Set the labels at the center of the window.	`False`

Returns:

Type	Description
`Self`	A new series.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> data = [1.0, 2.0, 3.0, 4.0]
>>> s_pd = pd.Series(data)
>>> s_pl = pl.Series(data)
>>> s_pa = pa.chunked_array([data])

We define a library agnostic function:

>>> def agnostic_rolling_sum(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.rolling_sum(window_size=2).to_native()

We can then pass any supported library such as Pandas, Polars, or PyArrow to func:

>>> agnostic_rolling_sum(s_pd)
0    NaN
1    3.0
2    5.0
3    7.0
dtype: float64

>>> agnostic_rolling_sum(s_pl)
shape: (4,)
Series: '' [f64]
[
   null
   3.0
   5.0
   7.0
]

>>> agnostic_rolling_sum(s_pa)
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    null,
    3,
    5,
    7
  ]
]

`rolling_var(window_size, *, min_periods=None, center=False, ddof=1)`

Apply a rolling variance (moving variance) over the values.

Warning

This functionality is considered unstable. It may be changed at any point without it being considered a breaking change.

A window of length window_size will traverse the values. The resulting values will be aggregated to their variance.

The window at a given row will include the row itself and the window_size - 1 elements before it.

Parameters:

Name	Type	Description	Default
`window_size`	`int`	The length of the window in number of elements. It must be a strictly positive integer.	required
`min_periods`	`int \| None`	The number of values in the window that should be non-null before computing a result. If set to `None` (default), it will be set equal to `window_size`. If provided, it must be a strictly positive integer, and less than or equal to `window_size`.	`None`
`center`	`bool`	Set the labels at the center of the window.	`False`
`ddof`	`int`	Delta Degrees of Freedom; the divisor for a length N window is N - ddof.	`1`

Returns:

Type	Description
`Self`	A new series.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> data = [1.0, 3.0, 1.0, 4.0]
>>> s_pd = pd.Series(data)
>>> s_pl = pl.Series(data)
>>> s_pa = pa.chunked_array([data])

We define a library agnostic function:

>>> def agnostic_rolling_var(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.rolling_var(window_size=2, min_periods=1).to_native()

We can then pass any supported library such as Pandas, Polars, or PyArrow to func:

>>> agnostic_rolling_var(s_pd)
0    NaN
1    2.0
2    2.0
3    4.5
dtype: float64

>>> agnostic_rolling_var(s_pl)
shape: (4,)
Series: '' [f64]
[
   null
   2.0
   2.0
   4.5
]

>>> agnostic_rolling_var(s_pa)
<pyarrow.lib.ChunkedArray object at ...>
[
  [
    nan,
    2,
    2,
    4.5
  ]
]

`round(decimals=0)`

Round underlying floating point data by decimals digits.

Parameters:

Name	Type	Description	Default
`decimals`	`int`	Number of decimals to round by.	`0`

Notes

For values exactly halfway between rounded decimal values pandas behaves differently than Polars and Arrow.

pandas rounds to the nearest even value (e.g. -0.5 and 0.5 round to 0.0, 1.5 and 2.5 round to 2.0, 3.5 and 4.5 to 4.0, etc..).

Polars and Arrow round away from 0 (e.g. -0.5 to -1.0, 0.5 to 1.0, 1.5 to 2.0, 2.5 to 3.0, etc..).

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> data = [1.12345, 2.56789, 3.901234]
>>> s_pd = pd.Series(data)
>>> s_pl = pl.Series(data)

Let's define a dataframe-agnostic function that rounds to the first decimal:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.round(1).to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    1.1
1    2.6
2    3.9
dtype: float64

>>> my_library_agnostic_function(s_pl)
shape: (3,)
Series: '' [f64]
[
   1.1
   2.6
   3.9
]

`sample(n=None, *, fraction=None, with_replacement=False, seed=None)`

Sample randomly from this Series.

Parameters:

Name	Type	Description	Default
`n`	`int \| None`	Number of items to return. Cannot be used with fraction.	`None`
`fraction`	`float \| None`	Fraction of items to return. Cannot be used with n.	`None`
`with_replacement`	`bool`	Allow values to be sampled more than once.	`False`
`seed`	`int \| None`	Seed for the random number generator. If set to None (default), a random seed is generated for each sample operation.	`None`

Notes

The sample method returns a Series with a specified number of randomly selected items chosen from this Series. The results are not consistent across libraries.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl

>>> s_pd = pd.Series([1, 2, 3, 4])
>>> s_pl = pl.Series([1, 2, 3, 4])

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.sample(fraction=1.0, with_replacement=True).to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
   a
2  3
1  2
3  4
3  4
>>> my_library_agnostic_function(s_pl)
shape: (4,)
Series: '' [i64]
[
   1
   4
   3
   4
]

`scatter(indices, values)`

Set value(s) at given position(s).

Parameters:

Name	Type	Description	Default
`indices`	`int \| Sequence[int]`	Position(s) to set items at.	required
`values`	`Any`	Values to set.	required

Note

This method always returns a new Series, without modifying the original one. Using this function in a for-loop is an anti-pattern, we recommend building up your positions and values beforehand and doing an update in one go.

For example, instead of

for i in [1, 3, 2]:
    value = some_function(i)
    s = s.scatter(i, value)

prefer

positions = [1, 3, 2]
values = [some_function(x) for x in positions]
s = s.scatter(positions, values)

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoFrameT
>>> data = {"a": [1, 2, 3], "b": [4, 5, 6]}
>>> df_pd = pd.DataFrame(data)
>>> df_pl = pl.DataFrame(data)

We define a library agnostic function:

>>> def my_library_agnostic_function(df_native: IntoFrameT) -> IntoFrameT:
...     df = nw.from_native(df_native)
...     return df.with_columns(df["a"].scatter([0, 1], [999, 888])).to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(df_pd)
     a  b
0  999  4
1  888  5
2    3  6
>>> my_library_agnostic_function(df_pl)
shape: (3, 2)
┌─────┬─────┐
│ a   ┆ b   │
│ --- ┆ --- │
│ i64 ┆ i64 │
╞═════╪═════╡
│ 999 ┆ 4   │
│ 888 ┆ 5   │
│ 3   ┆ 6   │
└─────┴─────┘

`shift(n)`

Shift values by n positions.

Parameters:

Name	Type	Description	Default
`n`	`int`	Number of indices to shift forward. If a negative value is passed, values are shifted in the opposite direction instead.	required

Notes

pandas may change the dtype here, for example when introducing missing values in an integer column. To ensure, that the dtype doesn't change, you may want to use fill_null and cast. For example, to shift and fill missing values with 0 in a Int64 column, you could do:

s.shift(1).fill_null(0).cast(nw.Int64)

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s = [2, 4, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a dataframe-agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.shift(1).to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    NaN
1    2.0
2    4.0
dtype: float64
>>> my_library_agnostic_function(s_pl)
shape: (3,)
Series: '' [i64]
[
   null
   2
   4
]

`sort(*, descending=False, nulls_last=False)`

Sort this Series. Place null values first.

Parameters:

Name	Type	Description	Default
`descending`	`bool`	Sort in descending order.	`False`
`nulls_last`	`bool`	Place null values last instead of first.	`False`

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s = [5, None, 1, 2]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define library agnostic functions:

>>> def agnostic_sort(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.sort().to_native()

>>> def agnostic_sort_descending(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.sort(descending=True).to_native()

We can then pass either pandas or Polars to agnostic_sort:

>>> agnostic_sort(s_pd)
1    NaN
2    1.0
3    2.0
0    5.0
dtype: float64
>>> agnostic_sort(s_pl)
shape: (4,)
Series: '' [i64]
[
   null
   1
   2
   5
]
>>> agnostic_sort_descending(s_pd)
1    NaN
0    5.0
3    2.0
2    1.0
dtype: float64
>>> agnostic_sort_descending(s_pl)
shape: (4,)
Series: '' [i64]
[
   null
   5
   2
   1
]

`skew()`

Calculate the sample skewness of the Series.

Returns:

Type	Description
`Any`	The sample skewness of the Series.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import pyarrow as pa
>>> import narwhals as nw
>>> s = [1, 1, 2, 10, 100]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)
>>> s_pa = pa.array(s)

We define a library agnostic function:

>>> @nw.narwhalify
... def func(s):
...     return s.skew()

We can pass any supported library such as Pandas, Polars, or PyArrow to func:

>>> func(s_pd)
np.float64(1.4724267269058975)
>>> func(s_pl)
1.4724267269058975

Notes

The skewness is a measure of the asymmetry of the probability distribution. A perfectly symmetric distribution has a skewness of 0.

`std(*, ddof=1)`

Get the standard deviation of this Series.

Parameters:

Name	Type	Description	Default
`ddof`	`int`	"Delta Degrees of Freedom": the divisor used in the calculation is N - ddof, where N represents the number of elements.	`1`

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.std()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
np.float64(1.0)
>>> my_library_agnostic_function(s_pl)
1.0

`sum()`

Reduce this Series to the sum value.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.sum()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
np.int64(6)
>>> my_library_agnostic_function(s_pl)
6

`tail(n=10)`

Get the last n rows.

Parameters:

Name	Type	Description	Default
`n`	`int`	Number of rows to return.	`10`

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> data = list(range(10))
>>> s_pd = pd.Series(data)
>>> s_pl = pl.Series(data)

Let's define a dataframe-agnostic function that returns the last 3 rows:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.tail(3).to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
7    7
8    8
9    9
dtype: int64
>>> my_library_agnostic_function(s_pl)
shape: (3,)
Series: '' [i64]
[
   7
   8
   9
]

`to_arrow()`

Convert to arrow.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> import pyarrow as pa
>>> import pandas as pd
>>> import polars as pl
>>> data = [1, 2, 3, 4]
>>> s_pd = pd.Series(name="a", data=data)
>>> s_pl = pl.Series(name="a", values=data)

Let's define a dataframe-agnostic function that converts to arrow:

>>> def my_library_agnostic_function(s_native: IntoSeries) -> pa.Array:
...     s = nw.from_native(s_native, series_only=True)
...     return s.to_arrow()

>>> my_library_agnostic_function(s_pd)
<pyarrow.lib.Int64Array object at ...>
[
    1,
    2,
    3,
    4
]

>>> my_library_agnostic_function(s_pl)
<pyarrow.lib.Int64Array object at ...>
[
    1,
    2,
    3,
    4
]

`to_dummies(*, separator='_', drop_first=False)`

Get dummy/indicator variables.

Parameters:

Name	Type	Description	Default
`separator`	`str`	Separator/delimiter used when generating column names.	`'_'`
`drop_first`	`bool`	Remove the first category from the variable being encoded.	`False`

Notes

pandas and Polars handle null values differently. Polars distinguishes between NaN and Null, whereas pandas doesn't.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries, IntoDataFrame
>>> import pandas as pd
>>> import polars as pl
>>> data = [1, 2, 3]
>>> s_pd = pd.Series(data, name="a")
>>> s_pl = pl.Series("a", data)

Let's define a dataframe-agnostic function that rounds to the first decimal:

>>> def my_library_agnostic_function(
...     s_native: IntoSeries, drop_first: bool = False
... ) -> IntoDataFrame:
...     s = nw.from_native(s_native, series_only=True)
...     return s.to_dummies(drop_first=drop_first).to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
   a_1  a_2  a_3
0    1    0    0
1    0    1    0
2    0    0    1

>>> my_library_agnostic_function(s_pd, drop_first=True)
   a_2  a_3
0    0    0
1    1    0
2    0    1

>>> my_library_agnostic_function(s_pl)
shape: (3, 3)
┌─────┬─────┬─────┐
│ a_1 ┆ a_2 ┆ a_3 │
│ --- ┆ --- ┆ --- │
│ i8  ┆ i8  ┆ i8  │
╞═════╪═════╪═════╡
│ 1   ┆ 0   ┆ 0   │
│ 0   ┆ 1   ┆ 0   │
│ 0   ┆ 0   ┆ 1   │
└─────┴─────┴─────┘
>>> my_library_agnostic_function(s_pl, drop_first=True)
shape: (3, 2)
┌─────┬─────┐
│ a_2 ┆ a_3 │
│ --- ┆ --- │
│ i8  ┆ i8  │
╞═════╪═════╡
│ 0   ┆ 0   │
│ 1   ┆ 0   │
│ 0   ┆ 1   │
└─────┴─────┘

`to_frame()`

Convert to dataframe.

Returns:

Type	Description
`DataFrame[Any]`	A new DataFrame.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries, IntoDataFrame
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s, name="a")
>>> s_pl = pl.Series("a", s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries) -> IntoDataFrame:
...     s = nw.from_native(s_native, series_only=True)
...     return s.to_frame().to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
   a
0  1
1  2
2  3
>>> my_library_agnostic_function(s_pl)
shape: (3, 1)
┌─────┐
│ a   │
│ --- │
│ i64 │
╞═════╡
│ 1   │
│ 2   │
│ 3   │
└─────┘

`to_list()`

Convert to list.

Notes

This function converts to Python scalars. It's typically more efficient to keep your data in the format native to your original dataframe, so we recommend only calling this when you absolutely need to.

Returns:

Type	Description
`list[Any]`	A list of Python objects.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s, name="a")
>>> s_pl = pl.Series("a", s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.to_list()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
[1, 2, 3]
>>> my_library_agnostic_function(s_pl)
[1, 2, 3]

`to_numpy()`

Convert to numpy.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> import numpy as np
>>> from narwhals.typing import IntoSeries
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s, name="a")
>>> s_pl = pl.Series("a", s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries) -> np.ndarray:
...     s = nw.from_native(s_native, series_only=True)
...     return s.to_numpy()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
array([1, 2, 3]...)
>>> my_library_agnostic_function(s_pl)
array([1, 2, 3]...)

`to_pandas()`

Convert to pandas.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s, name="a")
>>> s_pl = pl.Series("a", s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries) -> pd.Series:
...     s = nw.from_native(s_native, series_only=True)
...     return s.to_pandas()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    1
1    2
2    3
Name: a, dtype: int64
>>> my_library_agnostic_function(s_pl)
0    1
1    2
2    3
Name: a, dtype: int64

`to_native()`

Convert Narwhals series to native series.

Returns:

Type	Description
`IntoSeriesT`	Series of class that user started with.

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    1
1    2
2    3
dtype: int64
>>> my_library_agnostic_function(s_pl)
shape: (3,)
Series: '' [i64]
[
    1
    2
    3
]

`unique(*, maintain_order=False)`

Returns unique values of the series.

Parameters:

Name	Type	Description	Default
`maintain_order`	`bool`	Keep the same order as the original series. This may be more expensive to compute. Settings this to `True` blocks the possibility to run on the streaming engine for Polars.	`False`

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> s = [2, 4, 4, 6]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

Let's define a dataframe-agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeriesT) -> IntoSeriesT:
...     s = nw.from_native(s_native, series_only=True)
...     return s.unique(maintain_order=True).to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
0    2
1    4
2    6
dtype: int64
>>> my_library_agnostic_function(s_pl)
shape: (3,)
Series: '' [i64]
[
   2
   4
   6
]

`value_counts(*, sort=False, parallel=False, name=None, normalize=False)`

Count the occurrences of unique values.

Parameters:

Name	Type	Description	Default
`sort`	`bool`	Sort the output by count in descending order. If set to False (default), the order of the output is random.	`False`
`parallel`	`bool`	Execute the computation in parallel. Used for Polars only.	`False`
`name`	`str \| None`	Give the resulting count column a specific name; if `normalize` is True defaults to "proportion", otherwise defaults to "count".	`None`
`normalize`	`bool`	If true gives relative frequencies of the unique values	`False`

Returns:

Type	Description
`DataFrame[Any]`	A new DataFrame.

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries, IntoDataFrame
>>> import pandas as pd
>>> import polars as pl
>>> s_pd = pd.Series([1, 1, 2, 3, 2], name="s")
>>> s_pl = pl.Series(values=[1, 1, 2, 3, 2], name="s")

Let's define a dataframe-agnostic function:

>>> def my_library_agnostic_function(s_native: IntoSeries) -> IntoDataFrame:
...     s = nw.from_native(s_native, series_only=True)
...     return s.value_counts(sort=True).to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(s_pd)
   s  count
0  1      2
1  2      2
2  3      1

>>> my_library_agnostic_function(s_pl)
shape: (3, 2)
┌─────┬───────┐
│ s   ┆ count │
│ --- ┆ ---   │
│ i64 ┆ u32   │
╞═════╪═══════╡
│ 1   ┆ 2     │
│ 2   ┆ 2     │
│ 3   ┆ 1     │
└─────┴───────┘

`var(*, ddof=1)`

Get the variance of this Series.

Parameters:

Name	Type	Description	Default
`ddof`	`int`	"Delta Degrees of Freedom": the divisor used in the calculation is N - ddof, where N represents the number of elements.	`1`

Examples:

>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> from narwhals.typing import IntoSeries
>>> s = [1, 2, 3]
>>> s_pd = pd.Series(s)
>>> s_pl = pl.Series(s)

We define a library agnostic function:

>>> def agnostic_var(s_native: IntoSeries):
...     s = nw.from_native(s_native, series_only=True)
...     return s.var()

We can then pass either pandas or Polars to func:

>>> agnostic_var(s_pd)
np.float64(1.0)
>>> agnostic_var(s_pl)
1.0

`zip_with(mask, other)`

Take values from self or other based on the given mask.

Where mask evaluates true, take values from self. Where mask evaluates false, take values from other.

Parameters:

Name	Type	Description	Default
`mask`	`Self`	Boolean Series	required
`other`	`Self`	Series of same type.	required

Examples:

>>> import narwhals as nw
>>> from narwhals.typing import IntoSeriesT
>>> import pandas as pd
>>> import polars as pl
>>> s1_pl = pl.Series([1, 2, 3, 4, 5])
>>> s2_pl = pl.Series([5, 4, 3, 2, 1])
>>> mask_pl = pl.Series([True, False, True, False, True])
>>> s1_pd = pd.Series([1, 2, 3, 4, 5])
>>> s2_pd = pd.Series([5, 4, 3, 2, 1])
>>> mask_pd = pd.Series([True, False, True, False, True])

Let's define a dataframe-agnostic function:

>>> def my_library_agnostic_function(
...     s1_native: IntoSeriesT, mask_native: IntoSeriesT, s2_native: IntoSeriesT
... ) -> IntoSeriesT:
...     s1 = nw.from_native(s1_native, series_only=True)
...     mask = nw.from_native(mask_native, series_only=True)
...     s2 = nw.from_native(s2_native, series_only=True)
...     return s1.zip_with(mask, s2).to_native()

We can then pass either pandas or Polars to func:

>>> my_library_agnostic_function(
...     s1_pl, mask_pl, s2_pl
... )
shape: (5,)
Series: '' [i64]
[
   1
   4
   3
   2
   5
]
>>> my_library_agnostic_function(s1_pd, mask_pd, s2_pd)
0    1
1    4
2    3
3    2
4    5
dtype: int64

narwhals.Series

dtype: DType property

implementation: Implementation property

name: str property

shape: tuple[int] property

__arrow_c_stream__(requested_schema=None)

__getitem__(idx)

__iter__()

abs()

alias(name)

all()

any()

arg_max()

arg_min()

arg_true()

cast(dtype)

clip(lower_bound=None, upper_bound=None)

count()

cum_count(*, reverse=False)

cum_max(*, reverse=False)

cum_min(*, reverse=False)

cum_prod(*, reverse=False)

cum_sum(*, reverse=False)

diff()

drop_nulls()

ewm_mean(*, com=None, span=None, half_life=None, alpha=None, adjust=True, min_periods=1, ignore_nulls=False)

fill_null(value=None, strategy=None, limit=None)

filter(other)

gather_every(n, offset=0)

head(n=10)

is_between(lower_bound, upper_bound, closed='both')

is_duplicated()

is_empty()

is_finite()

is_first_distinct()

is_in(other)

is_last_distinct()

is_null()

is_sorted(*, descending=False)

is_unique()

item(index=None)

len()

max()

mean()

median()

min()

mode()

n_unique()

null_count()

pipe(function, *args, **kwargs)

quantile(quantile, interpolation)

rename(name)

replace_strict(old, new=None, *, return_dtype=None)

rolling_mean(window_size, *, min_periods=None, center=False)

rolling_std(window_size, *, min_periods=None, center=False, ddof=1)

rolling_sum(window_size, *, min_periods=None, center=False)

rolling_var(window_size, *, min_periods=None, center=False, ddof=1)

round(decimals=0)

sample(n=None, *, fraction=None, with_replacement=False, seed=None)

scatter(indices, values)

shift(n)

sort(*, descending=False, nulls_last=False)

skew()

std(*, ddof=1)

sum()

tail(n=10)

to_arrow()

to_dummies(*, separator='_', drop_first=False)

to_frame()

to_list()

to_numpy()

to_pandas()

to_native()

unique(*, maintain_order=False)

value_counts(*, sort=False, parallel=False, name=None, normalize=False)

var(*, ddof=1)

zip_with(mask, other)

`narwhals.Series`

`dtype: DType` `property`

`implementation: Implementation` `property`

`name: str` `property`

`shape: tuple[int]` `property`

`__arrow_c_stream__(requested_schema=None)`

`getitem(idx)`

`iter()`

`abs()`

`alias(name)`

`all()`

`any()`

`arg_max()`

`arg_min()`

`arg_true()`

`cast(dtype)`

`clip(lower_bound=None, upper_bound=None)`

`count()`

`cum_count(*, reverse=False)`

`cum_max(*, reverse=False)`

`cum_min(*, reverse=False)`

`cum_prod(*, reverse=False)`

`cum_sum(*, reverse=False)`

`diff()`

`drop_nulls()`

`ewm_mean(*, com=None, span=None, half_life=None, alpha=None, adjust=True, min_periods=1, ignore_nulls=False)`

`fill_null(value=None, strategy=None, limit=None)`

`filter(other)`

`gather_every(n, offset=0)`

`head(n=10)`

`is_between(lower_bound, upper_bound, closed='both')`

`is_duplicated()`

`is_empty()`

`is_finite()`

`is_first_distinct()`

`is_in(other)`

`is_last_distinct()`

`is_null()`

`is_sorted(*, descending=False)`

`is_unique()`

`item(index=None)`

`len()`

`max()`

`mean()`

`median()`

`min()`

`mode()`

`n_unique()`

`null_count()`

`pipe(function, *args, **kwargs)`

`quantile(quantile, interpolation)`

`rename(name)`

`replace_strict(old, new=None, *, return_dtype=None)`

`rolling_mean(window_size, *, min_periods=None, center=False)`

`rolling_std(window_size, *, min_periods=None, center=False, ddof=1)`

`rolling_sum(window_size, *, min_periods=None, center=False)`

`rolling_var(window_size, *, min_periods=None, center=False, ddof=1)`

`round(decimals=0)`

`sample(n=None, *, fraction=None, with_replacement=False, seed=None)`

`scatter(indices, values)`

`shift(n)`

`sort(*, descending=False, nulls_last=False)`

`skew()`

`std(*, ddof=1)`

`sum()`

`tail(n=10)`

`to_arrow()`

`to_dummies(*, separator='_', drop_first=False)`

`to_frame()`

`to_list()`

`to_numpy()`

`to_pandas()`

`to_native()`

`unique(*, maintain_order=False)`

`value_counts(*, sort=False, parallel=False, name=None, normalize=False)`

`var(*, ddof=1)`

`zip_with(mask, other)`