API: create option to allow pandas to patch pickle.load/loads at runtime for compat

[jreback]

related #5661
maybe `io.pickle.compat = 'global/local``

where we only allow local changes to the UnPickler.

This is not destructive, just 'bad practive', but weighing against more usability

[ghost]

pandas was patching the stdlib on import?? that's really not ok.

It's wrong to provide any mechanism that hides that fact behind a innocent-looking option.
Users can monkey patch explicitly in their main thread of control, which forces them to
know exactly what they're doing and take responsibility for it.

It's unfortunate that fixing this broke code for users but it shouldn't be part of pandas.
Shouldn't propagate bad behavior for legacy reasons in this case IMO.

[jreback]

@y-p no ...not in the released version (and not currently) (well was for a very short period of time until the referenced PR)

[ghost]

Thank god for that. no. monkey. patching. :)

[jreback]

hahah! I hear ya...ok...closing this

[ghost]

I just got

./test_fast.sh 
Traceback (most recent call last):
  File "/bin/nosetests", line 9, in <module>
    load_entry_point('nose==1.3.0', 'console_scripts', 'nosetests')()
  File "/usr/lib/python2.7/site-packages/nose/core.py", line 118, in __init__
    **extra_args)
  File "/usr/lib64/python2.7/unittest/main.py", line 94, in __init__
    self.parseArgs(argv)
  File "/usr/lib/python2.7/site-packages/nose/core.py", line 169, in parseArgs
    self.createTests()
  File "/usr/lib/python2.7/site-packages/nose/core.py", line 183, in createTests
    self.test = self.testLoader.loadTestsFromNames(self.testNames)
  File "/usr/lib/python2.7/site-packages/nose/loader.py", line 468, in loadTestsFromNames
    plug_res = self.config.plugins.loadTestsFromNames(names, module)
  File "/usr/lib/python2.7/site-packages/nose/plugins/manager.py", line 99, in __call__
    return self.call(*arg, **kw)
  File "/usr/lib/python2.7/site-packages/nose/plugins/manager.py", line 179, in _loadTestsFromNames
    result = meth(names, module=module)
  File "/usr/lib/python2.7/site-packages/nose/plugins/testid.py", line 181, in loadTestsFromNames
    data = load(fh)
ValueError: unsupported pickle protocol: 3

with master.
nose saves a pickle files of test ids in the root dir, are you sure there's no funny business with pickle after importing pandas?

[jreback]

nope
you are trying to read a py3 pickle with py2
which doesn't work (reverse works of course)

[ghost]

makes perfect sense, thanks.