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JacksonTanBS opened this issue Jan 23, 2015 · 2 comments
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Opening Pickle Files using ma.dump in Python 3 #5491

JacksonTanBS opened this issue Jan 23, 2015 · 2 comments
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00 - Bug component: numpy.ma masked arrays

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@JacksonTanBS
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When using numpy.ma.dump to save a masked array in Python 3:

np.ma.dump(a, pathtofile)

I got the following error:

/home/btan1/.virtualenvs/python3.3/lib/python3.3/site-packages/numpy/ma/core.py in dump(a, F)
   7141     if not hasattr(F, 'readline'):
   7142         F = open(F, 'w')
-> 7143     return pickle.dump(a, F)
   7144 
   7145 def dumps(a):

TypeError: must be str, not bytes

This is with NumPy 1.9.1 and Python 3.3.2.

From what I found out, it is because in Python 3 pickle files has to be opened in binary mode, i.e. L7142 should be F = open(F, 'wb'). Indeed, if I were to change it to:

with open(pathtofile, 'wb') as f:
    pickle.dump(a, f)

the error goes away.
@eric-wieser eric-wieser mentioned this issue Nov 19, 2017
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@orbit-stabilizer orbit-stabilizer mentioned this issue Nov 19, 2017
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@eric-wieser eric-wieser mentioned this issue Dec 10, 2017
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@eric-wieser
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eric-wieser commented Dec 10, 2017 •
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Echoing my comments elsewhere:

Why on earth do any of these exist?

  • np.ma.dump
  • np.ma.load
  • np.ma.dumps
  • np.ma.loads

It seems pretty obvious to me that exposing a slightly-tweaked pickle api is not in scope for what ma should do, especially since these tweaks are broken on python 3 anyway (#5491).

Given that this is already broken on py3, I vote we leave it broken and simply add

warnings.warn(
    "np.ma.{method} is deprecated, use pickle.{method} instead".format(method=the_method_name),
    DeprecationWarning)

Which I've done in #10192

This was referenced Dec 10, 2017
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eric-wieser added a commit to eric-wieser/numpy that referenced this issue Dec 11, 2017
@eric-wieser
DEP: Deprecate the pickle aliases
b023d73 
* The np.ma functions are misleading, as they do not actually do anything special for ma.array
* The np.loads functions doesn't even have numpy-specific documentation, and does not behave consistently with `np.load`
* The string overloads of np.ma.load and np.ma.dump do not work well on python 3, as they make assumptions about whether a binary or text pickle file is used (numpygh-5491)
@eric-wieser
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Alright, closing as wont-fix - these functions will be deprecated in 1.15.0, as of #10192

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