[Python-Dev] interaction between locals, builtins and except clause

[Georg Brandl]

Lisandro Dalcin schrieb:
> Porting to Py3K, I modified a function like the followin, using a
> trick for it working in Py2.x .
> 
>     def __iter__(self):
>         if self == _mpi.INFO_NULL:
>             return
>         try:    range = xrange
>         except: pass
>         nkeys = _mpi.info_get_nkeys(self)
>         for nthkey in range(nkeys):
>             yield _mpi.info_get_nthkey(self, nthkey)
> 
> However, I've got in my unittests (running with py3k)
> 
> ERROR: testPyMethods (__main__.TestInfo)
> ----------------------------------------------------------------------
> Traceback (most recent call last):
>   File "tests/unittest/test_info.py", line 123, in testPyMethods
>     for key in INFO:
>   File "/u/dalcinl/lib/python/mpi4py/MPI.py", line 937, in __iter__
>     for nthkey in range(nkeys):
> UnboundLocalError: local variable 'range' referenced before assignment
> 
> 
> I am not completelly sure if this is expected (it is, regarding
> implementation, but perhaps not regarding Python as a language),  so
> I post this for your consideration.

Yes, this is expected. By an assignment to range anywhere in a function
scope, the name is marked as a local and won't ever be looked up in the
global namespace.

I'd move the range = xrange part at the module top, or just bring the 2.x
version in a state where one run of 2to3 produces a working 3.0 version.

HTH,
Georg

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