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import pandas as pd df = pd.DataFrame([[1, 2, 3], [2, 2, 3]], columns=['a', 'b', 'c']) def t(df): print(df) print('-' * 10) return None g = df.groupby(by=['a', 'b']) g.apply(t) print(g.groups) g.apply(lambda x:print(x.index))
The function is invoked by 'apply' three times while there are only two groups.
The function is only invoked once by 'apply' for each group.
pd.show_versions()
commit: None python: 3.6.2.final.0 python-bits: 64 OS: Linux OS-release: 4.4.0-119-generic machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_HK.UTF-8 LOCALE: en_HK.UTF-8
pandas: 0.21.0 pytest: 3.2.1 pip: 9.0.1 setuptools: 36.4.0 Cython: None numpy: 1.14.3 scipy: None pyarrow: None xarray: None IPython: None sphinx: None patsy: None dateutil: 2.7.3 pytz: 2018.4 blosc: None bottleneck: None tables: None numexpr: 2.6.5 feather: None matplotlib: None openpyxl: 2.4.9 xlrd: None xlwt: None xlsxwriter: None lxml: None bs4: None html5lib: 0.999999999 sqlalchemy: 1.1.15 pymysql: None psycopg2: 2.7.3.1 (dt dec pq3 ext lo64) jinja2: 2.9.6 s3fs: None fastparquet: None pandas_gbq: None pandas_datareader: None
The text was updated successfully, but these errors were encountered:
cc @jreback
Sorry, something went wrong.
maybe similar to #2656
@Shawlf : Thanks for pointing this out! I had a feeling this wasn't a new thing...
#2936 looks like a better one to point to.
@jreback : A duplicate perhaps?
This is a documented implementation detail that it will call the function twice on the first group. See http://pandas.pydata.org/pandas-docs/stable/generated/pandas.core.groupby.GroupBy.apply.html and red box at end of https://pandas.pydata.org/pandas-docs/stable/groupby.html#flexible-apply
(if I missed something why this case would be different, please note)
@jorisvandenbossche : Does a similar comment apply to #2936?
That is already mentioned there, and for now #2936 is kept open as the issue to potentially improve this (add a keyword to specify the path instead of trying / calling the function twice, ...)
Successfully merging a pull request may close this issue.
Code Sample, a copy-pastable example if possible
Problem description
The function is invoked by 'apply' three times while there are only two groups.
Expected Output
The function is only invoked once by 'apply' for each group.
Output of
pd.show_versions()
[paste the output of
pd.show_versions()
here below this line]INSTALLED VERSIONS
commit: None
python: 3.6.2.final.0
python-bits: 64
OS: Linux
OS-release: 4.4.0-119-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_HK.UTF-8
LOCALE: en_HK.UTF-8
pandas: 0.21.0
pytest: 3.2.1
pip: 9.0.1
setuptools: 36.4.0
Cython: None
numpy: 1.14.3
scipy: None
pyarrow: None
xarray: None
IPython: None
sphinx: None
patsy: None
dateutil: 2.7.3
pytz: 2018.4
blosc: None
bottleneck: None
tables: None
numexpr: 2.6.5
feather: None
matplotlib: None
openpyxl: 2.4.9
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: 0.999999999
sqlalchemy: 1.1.15
pymysql: None
psycopg2: 2.7.3.1 (dt dec pq3 ext lo64)
jinja2: 2.9.6
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None
The text was updated successfully, but these errors were encountered: