Pickling support for finite word defined by callable and iterable

[slabbe]

Currently pickling doesn't work for finite word defined by iterator and callable :

sage: w = Word(iter('abcdefghijkl'))
sage: loads(dumps(w))
Traceback (most recent call last):
...
PicklingError: Can't pickle <type 'generator'>: attribute lookup __builtin__.generator failed

This is not too hard to support. One just have to expand the iterator to a list (or a tuple?) and save the list instead:

sage: w = Word(iter('abcdefghijkl'))
sage: loads(dumps(w))
word: abcdefghijkl
sage: type(_)
<class 'sage.combinat.words.word.FiniteWord_list'>

This is more general solution to the problem solved in #7519.

[slabbe]

The patch save those finite words to list. I wonder if tuple is better or is the same?

[slabbe]

I just uploaded the patch. Pickle is now supported for infinite word defined from a function :

sage: w = Word(lambda n:n)
sage: loads(dumps(w))
word: 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,...

It uses the pickle_function and unpickle_function (which gives a new utility for datatype argument)

sage: lambda n:n
<function <lambda> at 0x887e764>
sage: pickle_function(_)
"csage.misc.fpickle\ncode_ctor\np1\n(I1\nI1\nI1\nI67\nS'|\\x00\\x00S'\np2\n(t(t(S'n'\ntp3\nS'<ipython console>'\np4\nS'<lambda>'\np5\nI1\nS''\ntRp6\n."
sage: Word(_, datatype='pickled_function')
word: 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,...

Since pickle_function fails on CallableFromListOfWords, those finite words are expanded as a list in order to be saved:

sage: w = Word(range(5)) * Word('abcde')
sage: type(w)
<class 'sage.combinat.words.word.FiniteWord_callable_with_caching'>
sage: z = loads(dumps(w))
sage: z
word: 01234abcde
sage: type(z)
<class 'sage.combinat.words.word.FiniteWord_list'>

Needs review!!

[slabbe]

Forget about this patch!

[slabbe]

Depends on #7520.

[saliola]

Hello Sebastien. I've taken a look at the patch. Great changes! We can now pickle objects that we could not have pickled before.

The patch applies cleanly to sage-4.3.3 and all tests passed for make test.

[mvngu]

Merged ​trac_7619_pickle_for_FiniteWord_iter_callable-sl.patch.