PyCQA / PyCQA/pyflakes

erroneous 'undefined name' in exception handling + lambda

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Description

Original report by toikarin (@toikarin?) on Launchpad:


$ cat pyflakes-test.py 
try:
    raise Exception("test")
except Exception as e:
    print(e)
    x = lambda: e
    print(x)
    print(x())

$ pyflakes --version
1.5.0

$ pyflakes pyflakes-test.py
pyflakes-test.py:5: undefined name 'e'

running this with older pyflakes seems to work OK:

$ pyflakes --version
0.8.1

$ pyflakes pyflakes-test.py && echo $?
0

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by running the supplied pyflakes-test.py example and comparing the reported result with the older 0.8.1 behavior. Trace how pyflakes handles the exception-bound name e when it is referenced inside the lambda. Done means the current example no longer reports an erroneous undefined-name warning while preserving the other checks.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
devtools
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
38/100

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