mathtick mathtick - 1 month ago 27
Python Question

pandas.DataFrame.load/save between python2 and python3: pickle protocol issues

I haven't figure out how to do pickle load/save's between python 2 and 3 with pandas DataFrames. There is a 'protocol' option in the pickler that I've played with unsuccessfully but I'm hoping someone has a quick idea for me to try. Here is the code to get the error:

python2.7

>>> import pandas; from pylab import *
>>> a = pandas.DataFrame(randn(10,10))
>>> a.save('a2')
>>> a = pandas.DataFrame.load('a2')
>>> a = pandas.DataFrame.load('a3')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python2.7/site-packages/pandas-0.10.1-py2.7-linux-x86_64.egg/pandas/core/generic.py", line 30, in load
return com.load(path)
File "/usr/local/lib/python2.7/site-packages/pandas-0.10.1-py2.7-linux-x86_64.egg/pandas/core/common.py", line 1107, in load
return pickle.load(f)
ValueError: unsupported pickle protocol: 3


python3

>>> import pandas; from pylab import *
>>> a = pandas.DataFrame(randn(10,10))
>>> a.save('a3')
>>> a = pandas.DataFrame.load('a3')
>>> a = pandas.DataFrame.load('a2')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python3.3/site-packages/pandas-0.10.1-py3.3-linux-x86_64.egg/pandas/core/generic.py", line 30, in load
return com.load(path)
File "/usr/local/lib/python3.3/site-packages/pandas-0.10.1-py3.3-linux-x86_64.egg/pandas/core/common.py", line 1107, in load
return pickle.load(f)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xf4 in position 0: ordinal not in range(128)


Maybe expecting pickle to work between python version is a bit optimistic?

Answer

I had the same problem. You can change the protocol of the dataframe pickle file with the following function in python3: import pickle def change_pickle_protocol(filepath,protocol=2): with open(filepath,'rb') as f: obj = pickle.load(f) with open(filepath,'wb') as f: pickle.dump(obj,f,protocol=protocol) Then you should be able to open it in python2 no problem.

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