New submission from Ram Rachum <cool...@cool-rr.com>:
Please allow to deepcopy and to pickle paused generators, including all their
state.
This is implemented in Pypy:
Python 2.5.2 (335e875cb0fe, Dec 28 2010, 20:31:56)
[PyPy 1.4.1] on win32
Type "copyright", "credits" or "license()" for more information.
DreamPie 1.1.1
>>> import pickle, copy
>>> def next(thing): # For compatibility
... return thing.next()
>>> def g():
... for i in range(4):
... yield i
>>> list(g())
[0, 1, 2, 3]
>>> live_generator = g()
>>> next(live_generator)
0
>>> next(live_generator)
1
Now `live_generator` holds a generator which is in the middle of its operation.
It went through 0 and 1, and it still has 2 and 3 to yield.
We deepcopy it:
>>> live_generator_deepcopy = copy.deepcopy(live_generator)
The deepcopied generator assumes the same state of the original one. Let's
exhaust it:
>>> list(live_generator_deepcopy)
[2, 3]
>>> list(live_generator_deepcopy)
[]
Pypy also lets us pickle and unpickle the live generator:
>>> live_generator_pickled = pickle.dumps(live_generator)
>>> live_generator_unpickled = pickle.loads(live_generator_pickled)
>>> list(live_generator_unpickled)
[2, 3]
>>> list(live_generator_unpickled)
[]
And the original live generator was unchanged by all these operations:
>>> list(live_generator)
[2, 3]
>>> list(live_generator)
[]
All the above was demonstrated in Pypy. In Python 3.2, trying to pickle a live
generator raises this exception:
>>> pickle.dumps(live_generator)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
_pickle.PicklingError: Can't pickle <class 'generator'>: attribute
lookup builtins.generator failed
And trying to deepcopy one raises this exception:
>>> copy.deepcopy(live_generator)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "c:\Python32\lib\copy.py", line 174, in deepcopy
y = _reconstruct(x, rv, 1, memo)
File "c:\Python32\lib\copy.py", line 285, in _reconstruct
y = callable(*args)
File "c:\Python32\lib\copyreg.py", line 88, in __newobj__
return cls.__new__(cls, *args)
TypeError: object.__new__(generator) is not safe, use
generator.__new__()
It would be nice if Python 3.2 could pickle and deepcopy live generators.
----------
components: Library (Lib)
messages: 129213
nosy: cool-RR
priority: normal
severity: normal
status: open
title: Allow deepcopying and pickling paused generators
type: feature request
versions: Python 3.3
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue11299>
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