[Cython] ComprehensionNode problem

Vitja Makarov vitja.makarov at gmail.com
Fri Sep 2 08:06:50 CEST 2011

2011/9/2 Robert Bradshaw <robertwb at math.washington.edu>:
> On Sun, Aug 28, 2011 at 1:19 PM, Vitja Makarov <vitja.makarov at gmail.com> wrote:
>> I've started #715 ticket investigation.
>> Here is minimal test case:
>> # cython: language_level=3
>> def foo(target):
>>    return [(e for e in t) for t in target]
>> Crash in the ticket is related to GeneratorExpressionScope (name is
>> not correct, actually ScopedExprScope or NestedScope)
>> If you set languange_level to 2 you will see next error:
>> ...
>> Compiler crash traceback from this point on:
>>  File "/home/vitja/work/cython-vitek-git/Cython/Compiler/ExprNodes.py",
>> line 7732, in __init__
>>    if not result_type.create_from_py_utility_code(env):
>> AttributeError: 'UnspecifiedType' object has no attribute
>> 'create_from_py_utility_code'
>> Since ComprehensionNode.append and ComprehensionNode.loop.body is the
>> same generator body is created twice in MarkClosureVisitor
>> So the issue could be solved in two ways:
>>  - Write special handler for ComprehensionNode in MarkClosureVisitor
>>  - Remove append child attribute from ComprehensionNode (it can be
>> removed completely or just from children attribute list)
> +1 to the latter option (which I see is what you did, thanks).


I've also found one interesting bug in genexpr implementation


In CPython iterator is evaluated before genexpr is created.

class Foo:
    def __iter__(self):
        print 'iter'
        return self

    def next(self):
        return 1

g = (i for i in Foo())
print g

will print in cpython:
<generator ...>

and in cython:

Don't know how to deal with it now.


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