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pola-rs
GitHub Repository: pola-rs/polars
 Path: blob/main/docs/source/src/python/user-guide/expressions/column-selections.py
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# --8<-- [start:selectors_df]

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from datetime import date, datetime

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import polars as pl

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df = pl.DataFrame(

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    {

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        "id": [9, 4, 2],

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        "place": ["Mars", "Earth", "Saturn"],

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        "date": pl.date_range(date(2022, 1, 1), date(2022, 1, 3), "1d", eager=True),

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        "sales": [33.4, 2142134.1, 44.7],

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        "has_people": [False, True, False],

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        "logged_at": pl.datetime_range(

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            datetime(2022, 12, 1), datetime(2022, 12, 1, 0, 0, 2), "1s", eager=True

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        ),

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    }

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).with_row_index("index")

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print(df)

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# --8<-- [end:selectors_df]

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# --8<-- [start:all]

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out = df.select(pl.col("*"))

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# Is equivalent to

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out = df.select(pl.all())

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print(out)

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# --8<-- [end:all]

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# --8<-- [start:exclude]

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out = df.select(pl.col("*").exclude("logged_at", "index"))

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print(out)

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# --8<-- [end:exclude]

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# --8<-- [start:expansion_by_names]

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out = df.select(pl.col("date", "logged_at").dt.to_string("%Y-%h-%d"))

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print(out)

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# --8<-- [end:expansion_by_names]

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# --8<-- [start:expansion_by_regex]

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out = df.select(pl.col("^.*(as|sa).*$"))

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print(out)

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# --8<-- [end:expansion_by_regex]

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# --8<-- [start:expansion_by_dtype]

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out = df.select(pl.col(pl.Int64, pl.UInt32, pl.Boolean).n_unique())

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print(out)

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# --8<-- [end:expansion_by_dtype]

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# --8<-- [start:selectors_intro]

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import polars.selectors as cs

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out = df.select(cs.integer(), cs.string())

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print(out)

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# --8<-- [end:selectors_intro]

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# --8<-- [start:selectors_diff]

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out = df.select(cs.numeric() - cs.first())

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print(out)

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# --8<-- [end:selectors_diff]

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# --8<-- [start:selectors_union]

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out = df.select(cs.by_name("index") | ~cs.numeric())

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print(out)

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# --8<-- [end:selectors_union]

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# --8<-- [start:selectors_by_name]

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out = df.select(cs.contains("index"), cs.matches(".*_.*"))

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print(out)

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# --8<-- [end:selectors_by_name]

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# --8<-- [start:selectors_to_expr]

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out = df.select(cs.temporal().as_expr().dt.to_string("%Y-%h-%d"))

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print(out)

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# --8<-- [end:selectors_to_expr]

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# --8<-- [start:selectors_is_selector_utility]

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from polars.selectors import is_selector

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out = cs.numeric()

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print(is_selector(out))

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out = cs.boolean() | cs.numeric()

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print(is_selector(out))

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out = cs.numeric() + pl.lit(123)

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print(is_selector(out))

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# --8<-- [end:selectors_is_selector_utility]

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# --8<-- [start:selectors_colnames_utility]

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from polars.selectors import expand_selector

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out = cs.temporal()

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print(expand_selector(df, out))

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out = ~(cs.temporal() | cs.numeric())

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print(expand_selector(df, out))

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# --8<-- [end:selectors_colnames_utility]

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