[Pandas-dev] Deprecation of using a dict in groupby().agg({...}) to rename resulting columns
Joris Van den Bossche
jorisvandenbossche at gmail.com
Wed Apr 12 09:20:52 EDT 2017
Hi all,
As a heads up, we are deprecating the use of a dictionary in the agg method
on groupby/resample/rolling objects.
Basic example:
In [1]: df = pd.DataFrame({'A': [1, 1, 1, 2, 2],
...: 'B': range(5),
...: 'C':range(5)})
In [3]: df.groupby('A').B.agg({'foo': 'count'})
Out[3]:
foo
A
1 3
2 2
The above will be deprecated (and removed in a future version).
The documentation added in https://github.com/pandas-dev/pandas/pull/15931
gives a more detailed explanation of the reasoning, but basically it is to
clean up the API: now you can use dicts both to specify a aggregation
function for a specific column (for dataframes) as to rename the result
(series, or dataframes with nested dict), which is a confusing double use
of dicts.
The PR will be merged shortly, but the 0.20 release is still a few weeks
off, so certainly still time to give feedback. Which is certainly welcome!
Regards,
Joris
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