Description
Code Sample, a copy-pastable example if possible
df = pd.DataFrame({'A' : ['foo', 'bar', 'foo', 'bar'], 'B' : [1, 2, 3, 4]})
grouped = df.groupby('A')
print(grouped.apply(lambda x: x))
grouped.first()
print(grouped.apply(lambda x: x))Output:
A B
0 foo 1
1 bar 2
2 foo 3
3 bar 4
B
0 1
1 2
2 3
3 4
Problem description
The invoking method, without re-assignment of result or specifying that it should work in place, should not affect the object upon which it is being called.
Expected Output
A B
0 foo 1
1 bar 2
2 foo 3
3 bar 4
A B
0 foo 1
1 bar 2
2 foo 3
3 bar 4
Output of pd.show_versions()
INSTALLED VERSIONS
commit : None
python : 3.6.7.final.0
python-bits : 64
OS : Linux
OS-release : 4.15.0-62-generic
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8
pandas : 0.25.0
numpy : 1.17.0
pytz : 2019.2
dateutil : 2.8.0
pip : 19.2.1
setuptools : 40.6.3
Cython : 0.27.3
pytest : 3.0.7
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : 4.2.6
html5lib : None
pymysql : None
psycopg2 : 2.7.3.2 (dt dec pq3 ext lo64)
jinja2 : 2.10
IPython : 7.2.0
pandas_datareader: None
bs4 : 4.6.3
bottleneck : None
fastparquet : None
gcsfs : None
lxml.etree : 4.2.6
matplotlib : 2.0.2
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : 0.11.0
pyarrow : 0.13.0
pytables : None
s3fs : None
scipy : 1.0.0
sqlalchemy : 1.3.7
tables : None
xarray : None
xlrd : None
xlwt : None
xlsxwriter : None