narwhals.dtypes
Array
Fixed length list type.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
inner
|
DType | type[DType]
|
The datatype of the values within each array. |
required |
shape
|
int | tuple[int, ...]
|
The shape of the arrays. |
required |
Examples:
>>> import polars as pl
>>> import narwhals as nw
>>> s_native = pl.Series([[1, 2], [3, 4], [5, 6]], dtype=pl.Array(pl.Int32, 2))
>>> nw.from_native(s_native, series_only=True).dtype
Array(Int32, shape=(2,))
Decimal
Decimal type.
Examples:
>>> import polars as pl
>>> import narwhals as nw
>>> s = pl.Series(["1.5"], dtype=pl.Decimal)
>>> nw.from_native(s, series_only=True).dtype
Decimal
List
Variable length list type.
Examples:
>>> import pandas as pd
>>> import pyarrow as pa
>>> import narwhals as nw
>>> s_native = pd.Series(
... [["narwhal", "orca"], ["beluga", "vaquita"]],
... dtype=pd.ArrowDtype(pa.large_list(pa.large_string())),
... )
>>> nw.from_native(s_native, series_only=True).dtype
List(String)
Int128
128-bit signed integer type.
Int64
64-bit signed integer type.
Examples:
>>> import polars as pl
>>> import narwhals as nw
>>> s_native = pl.Series([2, 1, 3, 7])
>>> s = nw.from_native(s_native, series_only=True)
>>> s.cast(nw.Int64).dtype
Int64
Int32
32-bit signed integer type.
Examples:
>>> import pyarrow as pa
>>> import narwhals as nw
>>> s_native = pa.chunked_array([[2, 1, 3, 7]])
>>> s = nw.from_native(s_native, series_only=True)
>>> s.cast(nw.Int32).dtype
Int32
Int16
16-bit signed integer type.
Examples:
>>> import polars as pl
>>> import narwhals as nw
>>> s_native = pl.Series([2, 1, 3, 7])
>>> s = nw.from_native(s_native, series_only=True)
>>> s.cast(nw.Int16).dtype
Int16
Int8
8-bit signed integer type.
Examples:
>>> import pandas as pd
>>> import narwhals as nw
>>> s_native = pd.Series([2, 1, 3, 7])
>>> s = nw.from_native(s_native, series_only=True)
>>> s.cast(nw.Int8).dtype
Int8
IntegerType
Base class for integer data types.
UInt128
128-bit unsigned integer type.
UInt64
64-bit unsigned integer type.
Examples:
>>> import pandas as pd
>>> import narwhals as nw
>>> s_native = pd.Series([2, 1, 3, 7])
>>> s = nw.from_native(s_native, series_only=True)
>>> s.cast(nw.UInt64).dtype
UInt64
UInt32
32-bit unsigned integer type.
Examples:
>>> import polars as pl
>>> import narwhals as nw
>>> s_native = pl.Series([2, 1, 3, 7])
>>> s = nw.from_native(s_native, series_only=True)
>>> s.cast(nw.UInt32).dtype
UInt32
UInt16
16-bit unsigned integer type.
Examples:
>>> import polars as pl
>>> import narwhals as nw
>>> s_native = pl.Series([2, 1, 3, 7])
>>> s = nw.from_native(s_native, series_only=True)
>>> s.cast(nw.UInt16).dtype
UInt16
UInt8
8-bit unsigned integer type.
Examples:
>>> import polars as pl
>>> import narwhals as nw
>>> s_native = pl.Series([2, 1, 3, 7])
>>> s = nw.from_native(s_native, series_only=True)
>>> s.cast(nw.UInt8).dtype
UInt8
Field
Definition of a single field within a Struct
DataType.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
name
|
str
|
The name of the field within its parent |
required |
dtype
|
type[DType] | DType
|
The |
required |
Examples:
>>> import pyarrow as pa
>>> import narwhals as nw
>>> data = [{"a": 1, "b": ["narwhal", "beluga"]}, {"a": 2, "b": ["orca"]}]
>>> ser_pa = pa.chunked_array([data])
>>> nw.from_native(ser_pa, series_only=True).dtype.fields
[Field('a', Int64), Field('b', List(String))]
Float64
64-bit floating point type.
Examples:
>>> import pyarrow as pa
>>> import narwhals as nw
>>> s_native = pa.chunked_array([[0.001, 0.1, 0.01, 0.1]])
>>> s = nw.from_native(s_native, series_only=True)
>>> s.cast(nw.Float64).dtype
Float64
Float32
32-bit floating point type.
Examples:
>>> import polars as pl
>>> import narwhals as nw
>>> s_native = pl.Series([0.001, 0.1, 0.01, 0.1])
>>> s = nw.from_native(s_native, series_only=True)
>>> s.cast(nw.Float32).dtype
Float32
FloatType
Base class for float data types.
Boolean
Boolean type.
Examples:
>>> import pyarrow as pa
>>> import narwhals as nw
>>> s_native = pa.chunked_array([[True, False, False, True]])
>>> nw.from_native(s_native, series_only=True).dtype
Boolean
Categorical
A categorical encoding of a set of strings.
Examples:
>>> import polars as pl
>>> import narwhals as nw
>>> s_native = pl.Series(["beluga", "narwhal", "orca"])
>>> nw.from_native(s_native, series_only=True).cast(nw.Categorical).dtype
Categorical
Enum
A fixed categorical encoding of a unique set of strings.
Polars has an Enum data type, while pandas and PyArrow do not.
Examples:
>>> import polars as pl
>>> import narwhals as nw
>>> data = ["beluga", "narwhal", "orca"]
>>> s_native = pl.Series(data, dtype=pl.Enum(data))
>>> nw.from_native(s_native, series_only=True).dtype
Enum
NestedType
Base class for nested data types.
SignedIntegerType
Base class for signed integer data types.
String
UTF-8 encoded string type.
Examples:
>>> import pandas as pd
>>> import narwhals as nw
>>> s_native = pd.Series(["beluga", "narwhal", "orca", "vaquita"])
>>> nw.from_native(s_native, series_only=True).dtype
String
Struct
Struct composite type.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
fields
|
Sequence[Field] | Mapping[str, DType | type[DType]]
|
The fields that make up the struct. Can be either a sequence of Field objects or a mapping of column names to data types. |
required |
Examples:
>>> import pyarrow as pa
>>> import narwhals as nw
>>> s_native = pa.chunked_array(
... [[{"a": 1, "b": ["narwhal", "beluga"]}, {"a": 2, "b": ["orca"]}]]
... )
>>> nw.from_native(s_native, series_only=True).dtype
Struct({'a': Int64, 'b': List(String)})
to_schema() -> OrderedDict[str, DType | type[DType]]
Return Struct dtype as a schema dict.
Returns:
Type | Description |
---|---|
OrderedDict[str, DType | type[DType]]
|
Mapping from column name to dtype. |
Date
Data type representing a calendar date.
Examples:
>>> from datetime import date, timedelta
>>> import pyarrow as pa
>>> import narwhals as nw
>>> s_native = pa.chunked_array(
... [[date(2024, 12, 1) + timedelta(days=d) for d in range(4)]]
... )
>>> nw.from_native(s_native, series_only=True).dtype
Date
Datetime
Data type representing a calendar date and time of day.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
time_unit
|
TimeUnit
|
Unit of time. Defaults to |
'us'
|
time_zone
|
str | timezone | None
|
Time zone string, as defined in zoneinfo (to see valid strings run
|
None
|
Notes
Adapted from Polars implementation
Examples:
>>> from datetime import datetime, timedelta
>>> import polars as pl
>>> import narwhals as nw
>>> s_native = (
... pl.Series([datetime(2024, 12, 9) + timedelta(days=n) for n in range(5)])
... .cast(pl.Datetime("ms"))
... .dt.replace_time_zone("Africa/Accra")
... )
>>> nw.from_native(s_native, series_only=True).dtype
Datetime(time_unit='ms', time_zone='Africa/Accra')
Duration
Data type representing a time duration.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
time_unit
|
TimeUnit
|
Unit of time. Defaults to |
'us'
|
Notes
Adapted from Polars implementation
Examples:
>>> from datetime import timedelta
>>> import pyarrow as pa
>>> import narwhals as nw
>>> s_native = pa.chunked_array(
... [[timedelta(seconds=d) for d in range(1, 4)]], type=pa.duration("ms")
... )
>>> nw.from_native(s_native, series_only=True).dtype
Duration(time_unit='ms')
Object
Data type for wrapping arbitrary Python objects.
Examples:
>>> import pandas as pd
>>> import narwhals as nw
>>> class Foo: ...
>>> s_native = pd.Series([Foo(), Foo()])
>>> nw.from_native(s_native, series_only=True).dtype
Object
Unknown
Type representing DataType values that could not be determined statically.
Examples:
>>> import pandas as pd
>>> import narwhals as nw
>>> s_native = pd.Series(pd.period_range("2000-01", periods=4, freq="M"))
>>> nw.from_native(s_native, series_only=True).dtype
Unknown
UnsignedIntegerType
Base class for unsigned integer data types.
Time
Data type representing the time of day.
Examples:
>>> import polars as pl
>>> import pyarrow as pa
>>> import narwhals as nw
>>> import duckdb
>>> from datetime import time
>>> data = [time(9, 0), time(9, 1, 10), time(9, 2)]
>>> ser_pl = pl.Series(data)
>>> ser_pa = pa.chunked_array([pa.array(data, type=pa.time64("ns"))])
>>> rel = duckdb.sql(
... " SELECT * FROM (VALUES (TIME '12:00:00'), (TIME '14:30:15')) df(t)"
... )
>>> nw.from_native(ser_pl, series_only=True).dtype
Time
>>> nw.from_native(ser_pa, series_only=True).dtype
Time
>>> nw.from_native(rel).schema["t"]
Time
Binary
Binary type.
Examples:
>>> import polars as pl
>>> import narwhals as nw
>>> import pyarrow as pa
>>> import duckdb
>>> data = [b"test1", b"test2"]
>>> ser_pl = pl.Series(data, dtype=pl.Binary)
>>> ser_pa = pa.chunked_array([pa.array(data, type=pa.binary())])
>>> rel = duckdb.sql(
... "SELECT * FROM (VALUES (BLOB 'test1'), (BLOB 'test2')) AS df(t)"
... )
>>> nw.from_native(ser_pl, series_only=True).dtype
Binary
>>> nw.from_native(ser_pa, series_only=True).dtype
Binary
>>> nw.from_native(rel).schema["t"]
Binary