[pypy-dev] pickle/cPickle bug

[Maciej Fijalkowski]

Hi Martin.

This is a documented difference with CPython where files are not
flushed unless either closed explicitly or garbage collected (which
will happen later than you might expect).

On Wed, Apr 23, 2014 at 3:39 PM, Martin Koch <mak at issuu.com> wrote:
> Hi list
>
> I have found what appears to be a bug in the pickle and cPickle library in
> pypy. I can reproduce it both on linux and mac. Basically, I can't unpickle
> a file if it has been pickled with a file object returned by open(), but it
> works if I use the with construct. The problem is present both using pickle
> and cPickle.
>
> On mac, the pypy version is
> Python 2.7.3 (87aa9de10f9c, Nov 24 2013, 20:57:21)
> [PyPy 2.2.1 with GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.2.79)]
>
> On linux, the pypy version is
> Python 2.7.3 (2.2.1+dfsg-1, Jan 24 2014, 10:12:37)
> [PyPy 2.2.1 with GCC 4.6.3]
>
> #import cPickle as pickle
> import pickle
>
> l = range(10)
> # fails:
> try:
>     pickle.dump(l, open('f', 'wb'))
>     print pickle.load(open('f', 'rb'))
> except EOFError:
>     print("Yup, that's an EOFError")
>
>
> #succeeds
> with open('f', 'wb') as f:
>    pickle.dump(l, f)
>
> with open('f', 'rb') as f:
>    print pickle.load(f)
>
>
> If I instead of using open() inline in the argument to pickle assign it to a
> variable and explicitly close the file after calling pickle.dump, then the
> problem goes away:
>
>     f = open('f', 'wb')
>     pickle.dump(l, f)
>     f.close()
>     print pickle.load(open('f', 'rb'))
>
>
> Apparently, in the first code snippet, the file isn't closed as it should be
> when the object returned by open() goes out of scope after pickle.dump.
>
> Thanks,
> /Martin Koch
>
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