BUG: pd.read_pickle not backwards compatible from v2.1.0 to v1.3.4 · Issue #55137 · pandas-dev/pandas (original) (raw)

Pandas version checks

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• I have confirmed this bug exists on the latest version of pandas.
• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

in a pandas 1.3.4 environment

import pandas as pd import numpy as np

df = pd.DataFrame(np.ones((100, 4))) df.to_pickle("old_pandas.pkl")

in pandas 2.1.0 environment

import pandas as pd

df = pd.read_pickle("old_pandas.pkl")

Issue Description

The read_pickle method raises an error when attempting to read a file serialized with to_pickle in pandas 1.3.4. No error is raised when using 2.0. to read_pickle, or if the file is serialized with version >=1.4.

The documentation states the method should be backwards compatible to pandas 0.20.3 provided the object was serialized with to_pickle (as in this case).

Traceback (most recent call last):
  File "/home/me/envs/new_pandas/lib/python3.10/site-packages/pandas/io/pickle.py", line 206, in read_pickle
    return pickle.load(handles.handle)
  File "/home/me/envs/new_pandas/lib/python3.10/site-packages/pandas/core/internals/blocks.py", line 2400, in new_block
    return klass(values, ndim=ndim, placement=placement, refs=refs)
TypeError: Argument 'placement' has incorrect type (expected pandas._libs.internals.BlockPlacement, got slice)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/me/envs/new_pandas/lib/python3.10/site-packages/pandas/compat/pickle_compat.py", line 35, in load_reduce
    stack[-1] = func(*args)
  File "/home/me/envs/new_pandas/lib/python3.10/site-packages/pandas/core/internals/blocks.py", line 2400, in new_block
    return klass(values, ndim=ndim, placement=placement, refs=refs)
TypeError: Argument 'placement' has incorrect type (expected pandas._libs.internals.BlockPlacement, got slice)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/me/envs/new_pandas/lib/python3.10/site-packages/pandas/io/pickle.py", line 211, in read_pickle
    return pc.load(handles.handle, encoding=None)
  File "/home/me/envs/new_pandas/lib/python3.10/site-packages/pandas/compat/pickle_compat.py", line 225, in load
    return up.load()
  File "/usr/lib/python3.10/pickle.py", line 1213, in load
    dispatch[key[0]](self)
  File "/home/me/envs/new_pandas/lib/python3.10/site-packages/pandas/compat/pickle_compat.py", line 55, in load_reduce
    elif args and issubclass(args[0], PeriodArray):
TypeError: issubclass() arg 1 must be a class

Expected Behavior

Method should be backwards compatible, as per the documentation.

Installed Versions

INSTALLED VERSIONS

commit : f00efd0
python : 3.10.12.final.0
python-bits : 64
OS : Linux
OS-release : 5.15.0-78-generic
Version : #85-Ubuntu SMP Fri Jul 7 15:25:09 UTC 2023
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_GB.UTF-8
LOCALE : en_GB.UTF-8

pandas : 2.2.0dev0+225.gf00efd0344
numpy : 1.25.2
pytz : 2023.3.post1
dateutil : 2.8.2
setuptools : 59.6.0
pip : 22.0.2
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : None
IPython : None
pandas_datareader : None
bs4 : None
bottleneck : None
dataframe-api-compat: None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : None
numba : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pyreadstat : None
python-calamine : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
zstandard : None
tzdata : 2023.3
qtpy : None
pyqt5 : None

INSTALLED VERSIONS ------------------ commit : 945c9edpython : 3.10.12.final.0 python-bits : 64 OS : Linux OS-release : 5.15.0-78-generic Version : #85-Ubuntu SMP Fri Jul 7 15:25:09 UTC 2023 machine : x86_64 processor : x86_64 byteorder : little LC_ALL : None LANG : en_GB.UTF-8 LOCALE : en_GB.UTF-8

pandas : 1.3.4
numpy : 1.25.2
pytz : 2023.3.post1
dateutil : 2.8.2
pip : 22.0.2
setuptools : 59.6.0
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : None
IPython : None
pandas_datareader: None
bs4 : None
bottleneck : None
fsspec : None
fastparquet : None
gcsfs : None
matplotlib : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlwt : None
numba : None