narwhals.Expr.cat
get_categories()
Get unique categories from column.
Examples:
Let's create some dataframes:
>>> import pandas as pd
>>> import polars as pl
>>> import narwhals as nw
>>> data = {"fruits": ["apple", "mango", "mango"]}
>>> df_pd = pd.DataFrame(data, dtype="category")
>>> df_pl = pl.DataFrame(data, schema={"fruits": pl.Categorical})
We define a dataframe-agnostic function to get unique categories from column 'fruits':
>>> @nw.narwhalify
... def func(df):
... return df.select(nw.col("fruits").cat.get_categories())
We can then pass either pandas or Polars to func
:
>>> func(df_pd)
fruits
0 apple
1 mango
>>> func(df_pl)
shape: (2, 1)
┌────────┐
│ fruits │
│ --- │
│ str │
╞════════╡
│ apple │
│ mango │
└────────┘