Add `Selector.__xor__` (symmetric difference)

[dangotbanned]

Related

• Support set operations on selectors #224
• feat: implement selectors set arithmetic #247
• https://github.com/pola-rs/polars/blob/b9dd8cdbd6e6ec8373110536955ed5940b9460ec/crates/polars-plan/src/dsl/selector.rs#L10-L16
• https://docs.pola.rs/api/python/stable/reference/selectors.html#set-operations
• https://en.wikipedia.org/wiki/Symmetric_difference

Description

I can't seem to find this ever being discussed - but while working on modeling selectors in (#2572) it looks like we're missing 1 set operator (^).

Example from the polars docs:

import polars.selectors as cs
import polars as pl

# set up an empty dataframe with plenty of columns of various dtypes
df = pl.DataFrame(
    schema={
        "abc": pl.UInt16,
        "bbb": pl.UInt32,
        "cde": pl.Float64,
        "def": pl.Float32,
        "eee": pl.Boolean,
        "fgg": pl.Boolean,
        "ghi": pl.Time,
        "JJK": pl.Date,
        "Lmn": pl.Duration,
        "opp": pl.Datetime("ms"),
        "qqR": pl.String,
    },
)



# Select the SYMMETRIC DIFFERENCE of numeric columns and columns that contain an "e"
assert df.select(cs.contains("e") ^ cs.numeric()).schema == {
    "abc": UInt16,
    "bbb": UInt32,
    "eee": Boolean,
}

Considering that we do support the other 4 (&, |, -, ~) operators, it would round out the set nicely 😉

[MarcoGorelli]

Sure sounds good