Dict comprehensions fail in NamedTuple
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Nobody has claimed this yet.
bug
false-positive
priority-1-normal
semantic-analyzer
topic-named-tuple
- Dominant language
- Python
- Stars
- 20.6k
- Forks
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- PR merge metrics
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Description
from typing import Dict, Any, NamedTuple
def out() -> str:
return "out"
d = {"x": 0, "y": 1}
class Test(NamedTuple):
qwer: Dict[str, Any] = {k: v for k, v in d}
Fails mypy with error:
main.py:13: error: Name 'k' is not defined
main.py:13: error: Name 'v' is not defined
Found 2 errors in 1 file (checked 1 source file)
Oddly, removing the out function makes type checking work again:
from typing import Dict, Any, NamedTuple
d = {"x": 0, "y": 1}
class Test(NamedTuple):
qwer: Dict[str, Any] = {k: v for k, v in d}
Success: no issues found in 1 source file
Playground URL: https://mypy-play.net/?mypy=latest&python=3.8&gist=aa715bc0f6d14152487d753f3fa64885
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reproducing the supplied NamedTuple and dict-comprehension example with the linked mypy-play configuration. Trace the type checker's handling of NamedTuple defaults and comprehension scope, then add a regression test; done means the example type-checks without the undefined-name errors.
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
- 35/100