I'm trying to select a subset of a subset of a dataframe, selecting only some columns, and filtering on the rows.
df.loc[df.a.isin(['Apple', 'Pear', 'Mango']), ['a', 'b', 'f', 'g']]
However, I'm getting the error:
Passing list-likes to .loc or [] with any missing label will raise
KeyError in the future, you can use .reindex() as an alternative.
What 's the correct way to slice and filter now?
This is a change introduced in v0.21.1
, and has been explained in the docs at length -
Previously, selecting with a list of labels, where one or more labels were missing would always succeed, returning
NaN
for missing labels. This will now show aFutureWarning
. In the future this will raise aKeyError
(GH15747). This warning will trigger on aDataFrame
or aSeries
for using.loc[]
or[[]]
when passing a list-of-labels with at least 1 missing label.
For example,
df
A B C
0 7.0 NaN 8
1 3.0 3.0 5
2 8.0 1.0 7
3 NaN 0.0 3
4 8.0 2.0 7
Try some kind of slicing as you're doing -
df.loc[df.A.gt(6), ['A', 'C']]
A C
0 7.0 8
2 8.0 7
4 8.0 7
No problem. Now, try replacing C
with a non-existent column label -
df.loc[df.A.gt(6), ['A', 'D']]
FutureWarning: Passing list-likes to .loc or [] with any missing label will raise
KeyError in the future, you can use .reindex() as an alternative.
A D
0 7.0 NaN
2 8.0 NaN
4 8.0 NaN
So, in your case, the error is because of the column labels you pass to loc
. Take another look at them.