Closed
Description
-
I have checked that this issue has not already been reported.
-
I have confirmed this bug exists on the latest version of pandas.
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(optional) I have confirmed this bug exists on the master branch of pandas.
Code Sample, a copy-pastable example
In [44]: df = pd.DataFrame({"a": [3, 4]})
In [45]: df
Out[45]:
a
0 3
1 4
In [46]: mask = df["a"] > 0
In [47]: mask
Out[47]:
0 True
1 True
Name: a, dtype: bool
In [48]: df_a = df.loc[:, "a"]
In [49]: df_a["a"] = 1
In [50]: df_a
Out[50]:
0 3
1 4
a 1
Name: a, dtype: int64
In [51]: df.__dict__
Out[51]:
{'_is_copy': None,
'_mgr': BlockManager
Items: Index(['a'], dtype='object')
Axis 1: RangeIndex(start=0, stop=2, step=1)
IntBlock: slice(0, 1, 1), 1 x 2, dtype: int64,
'_item_cache': {'a': 0 3
1 4
a 1
Name: a, dtype: int64},
'_attrs': {}}
In [52]: mask
Out[52]:
0 True
1 True
Name: a, dtype: bool
In [53]: df
Out[53]:
a
0 3
1 4
In [54]: df.loc[mask, "a"]
---------------------------------------------------------------------------
AssertionError Traceback (most recent call last)
<ipython-input-54-e9cf788ed9f4> in <module>
----> 1 df.loc[mask, "a"]
~/miniconda3/envs/conduit-poetry/lib/python3.8/site-packages/pandas/core/indexing.py in __getitem__(self, key)
871 # AttributeError for IntervalTree get_value
872 pass
--> 873 return self._getitem_tuple(key)
874 else:
875 # we by definition only have the 0th axis
~/miniconda3/envs/conduit-poetry/lib/python3.8/site-packages/pandas/core/indexing.py in _getitem_tuple(self, tup)
1053 return self._multi_take(tup)
1054
-> 1055 return self._getitem_tuple_same_dim(tup)
1056
1057 def _get_label(self, label, axis: int):
~/miniconda3/envs/conduit-poetry/lib/python3.8/site-packages/pandas/core/indexing.py in _getitem_tuple_same_dim(self, tup)
751 # We should never have retval.ndim < self.ndim, as that should
752 # be handled by the _getitem_lowerdim call above.
--> 753 assert retval.ndim == self.ndim
754
755 return retval
AssertionError:
Problem description
By manipulating one column that was created by copying a part of the DataFrame, the cache for this one column is updated in the DataFrame. However, the cached data are not compatible with the DataFrame index and causes problems later, e.g. the AssertionError from the example.
Expected Output
Manipulating separate object would not influence the original object in a way that leads to AssertionError.
Output of pd.show_versions()
INSTALLED VERSIONS
------------------
commit : d9fff2792bf16178d4e450fe7384244e50635733
python : 3.8.3.final.0
python-bits : 64
OS : Linux
OS-release : 5.7.14-200.fc32.x86_64
Version : #1 SMP Fri Aug 7 23:16:37 UTC 2020
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8
pandas : 1.1.0
numpy : 1.19.1
pytz : 2020.1
dateutil : 2.8.1
pip : 20.1.1
setuptools : 49.2.0.post20200714
Cython : None
pytest : 6.0.1
hypothesis : None
sphinx : None
blosc : 1.9.1
feather : None
xlsxwriter : None
lxml.etree : 4.5.2
html5lib : 1.1
pymysql : None
psycopg2 : None
jinja2 : None
IPython : 7.17.0
pandas_datareader: None
bs4 : None
bottleneck : None
fsspec : 0.8.0
fastparquet : None
gcsfs : 0.6.2
matplotlib : None
numexpr : 2.7.1
odfpy : None
openpyxl : None
pandas_gbq : 0.11.0
pyarrow : None
pytables : None
pyxlsb : None
s3fs : None
scipy : 1.5.2
sqlalchemy : None
tables : 3.6.1
tabulate : None
xarray : None
xlrd : None
xlwt : None
numba : None