Cascading try/except imports report duplicates

[pyflakes-bot]

Original report by 4-launchpad-tim-thechases-com on Launchpad:

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With the attached example file, pyflakes reports

pf.py:6: redefinition of unused 'connect' from line 3
pf.py:6: redefinition of unused 'PARSE_DECLTYPES' from line 3
pf.py:6: redefinition of unused 'PARSE_COLNAMES' from line 3

They're not redefinitions, but fallbacks in case defining them the first time fails. I don't know if there's a way to catch this, but it's worth noting.

[pyflakes-bot]

Original comment by 4-launchpad-tim-thechases-com on Launchpad:

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[pyflakes-bot]

Original comment by adiroiban (@adiroiban?) on Launchpad:

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This is on the TODO list: pyflakes.test.test_imports.Test.test_tryingMultipleImports

[pyflakes-bot]

Original comment by fpinard on Launchpad:

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The same duplication warning occurs if one assigns the import name, like in:

try:
import signal
except ImportError:
signal = None

This code comes from a program which sometimes runs under Jython, so it could quickly test if "signal" was available.

François

[pyflakes-bot]

Original comment by saperski on Launchpad:

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I think I have a fix for this problem for a slightly different fork of pyflakes here: kevinw/pyflakes#28

[pyflakes-bot]

Original comment by zbyszek-in on Launchpad:

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Tested this on multi-import from http://lxml.de/tutorial.html and it seems to work well.

OTOH, stuff like:
choice = sys.getenv('CHOICE')
if choice == 'A':
import A as backend

if choice == 'B':
import B as backend

don't work, as expected.