Strange behaviour of pd.DataFrame.drop() with inplace argument (original) (raw)

Code Sample, a copy-pastable example if possible

input - 1

df = pd.DataFrame({}) df["x1"] = [1, 2, 3, 4, 5] df["x2"] = [0, 0, 0, 1, 1] df["target"] = [10, 20, 30, 40, 50] y = df["target"] df.drop("target", axis=1, inplace=True) y = y + np.min(y)

output df (without removed target column)

x1	x2

0 1 0 1 2 0 2 3 0 3 4 1 4 5 1

input - 2

df = pd.DataFrame({}) df["x1"] = [1, 2, 3, 4, 5] df["x2"] = [0, 0, 0, 1, 1] df["target"] = [10, 20, 30, 40, 50] y = df["target"] df.drop("target", axis=1, inplace=True) y += np.min(y)

output df (with the removed target column)

  | x1 | x2 | target -- | -- | -- | -- 0 | 1 | 0 | 20 1 | 2 | 0 | 30 2 | 3 | 0 | 40 3 | 4 | 1 | 50 4 | 5 | 1 | 60

Problem description

Pandas return DataFrame with removed column after doing in-place operation with a column. Is it a bug or intentional behavior?

Output of pd.show_versions()

Details

INSTALLED VERSIONS

commit : None

pandas : 0.25.1
numpy : 1.16.2
pytz : 2018.9
dateutil : 2.7.5
pip : 18.1
setuptools : 42.0.2
Cython : 0.29.2
pytest : 4.1.0
hypothesis : None
sphinx : 1.8.3
blosc : None
feather : None
xlsxwriter : 1.1.2
lxml.etree : 4.3.0
html5lib : 1.0.1
pymysql : None
psycopg2 : None
jinja2 : 2.10
IPython : 7.2.0
pandas_datareader: None
bs4 : 4.7.1
bottleneck : 1.2.1
fastparquet : None
gcsfs : None
lxml.etree : 4.3.0
matplotlib : 3.0.2
numexpr : 2.6.9
odfpy : None
openpyxl : 2.5.12
pandas_gbq : None
pyarrow : None
pytables : None
s3fs : None
scipy : 1.2.1
sqlalchemy : 1.2.15
tables : 3.4.4
xarray : 0.14.0
xlrd : 1.2.0
xlwt : 1.3.0
xlsxwriter : 1.1.2