2013/7/18 Eleytherios Stamatogiannakis <estama@gmail.com>
Why is there such a huge speed difference between cPickle.dump( ... f) and f.write(cPickle.dumps(...)) ?

Did you count the number of calls to f.write?
pickle call write() once per pickled object.

Now, pypy's implementation of buffered file uses a (RPython) list of strings, and does a final ''.join.
This is probably much less efficient than the RStringIO implementation.

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Amaury Forgeot d'Arc