REGR: Setting values with 'loc' and boolean mask mixes up values (all-True mask) · Issue #48701 · pandas-dev/pandas (original) (raw)

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Description

According to documentation, using loc should work with Boolean arrays. However, the following does not seem to work:

import pandas as pd

n = 17

data = pd.DataFrame({ "name": n * ["a"], "x": range(n), "y": range(n) })

copy = data.copy()

idx = n * [True] data.loc[idx, ["x", "y"]] = data[["x", "y"]] assert data.equals(copy) # Raises assertion error

The weird thing is that if n is smaller then the code works. This has been tested on Pandas 1.5.0