Question

我还没有弄清楚如何使用pandas DataFrames在python 2和3之间进行pickle加载/保存。有一个＆＃39;协议＆＃39;我在选手中选择的选项没有成功，但我希望有人能快速让我尝试。以下是获取错误的代码：

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)

也许期待在python版本之间工作的pickle有点乐观？

Answer 1

我遇到了同样的问题。您可以使用python3中的以下函数更改dataframe pickle文件的协议：

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)

然后你应该可以在python2中打开它没问题。

Answer 2

如果有人使用pandas.DataFrame.to_pickle()，请在源代码中进行以下修改，以具备pickle协议设置的能力：

1）在源文件/pandas/io/pickle.py中（修改前将原始文件复制为/pandas/io/pickle.py.ori）搜索以下行：

def to_pickle(obj, path):

pkl.dump(obj, f, protocol=pkl.HIGHEST_PROTOCOL)

将这些行更改为：

def to_pickle(obj, path, protocol=pkl.HIGHEST_PROTOCOL):

pkl.dump(obj, f, protocol=protocol)

2）在源文件/pandas/core/generic.py中（修改前将原始文件复制为/pandas/core/generic.py.ori），搜索以下行：

def to_pickle(self, path):

return to_pickle(self, path)

将这些行更改为：

def to_pickle(self, path, protocol=None):

return to_pickle(self, path, protocol)

3）如果python内核运行，请重新启动它，然后使用任何available pickle protocol（0,1,2,3,4）保存数据帧：

# Python 2.x can read this
df.to_pickle('my_dataframe.pck', protocol=2)

# protocol will be the highest (4), Python 2.x can not read this
df.to_pickle('my_dataframe.pck')

4）在pandas升级后，重复步骤1＆amp; 2。

5）（可选）要求开发人员在正式版本中具备此功能（因为您的代码将在没有这些更改的情况下在任何其他Python环境中抛出异常）

美好的一天！

Answer 3

您可以覆盖pickle包可用的最高协议：

import pickle as pkl
import pandas as pd
if __name__ == '__main__':
    # this constant is defined in pickle.py in the pickle package:"
    pkl.HIGHEST_PROTOCOL = 2
    # 'foo.pkl' was saved in pickle protocol 4
    df = pd.read_pickle(r"C:\temp\foo.pkl")

    # 'foo_protocol_2' will be saved in pickle protocol 2 
    # and can be read in pandas with Python 2
    df.to_pickle(r"C:\temp\foo_protocol_2.pkl")

这绝对不是一个优雅的解决方案，但它可以在不直接更改pandas代码的情况下完成工作。

更新：我发现新版本的pandas允许在.to_pickle函数中指定pickle版本： https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.to_pickle.html[1] DataFrame.to_pickle(path, compression='infer', protocol=4)

python2和python3之间的pandas.DataFrame.load / save：pickle协议问题

3 个答案: