Why is the dict extension prohibited in the TypedDict constructor?
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bug
topic-typed-dict
- Dominant language
- Python
- Stars
- 20.6k
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Description
Bug Report
Cannot use dict expansion in TypedDict constructor. Why?
To Reproduce
from typing import TypedDict
class SomeTypedDict(TypedDict):
field1: str
field2: int
field3: bool
SOME_SAMPLE = {
'field1': 'str',
'field2': 0,
'field3': True,
}
some_variable = SomeTypedDict(**SOME_SAMPLE)
print(some_variable)
Actual Behavior
user@pc:~/$ mypy main.py
main.py:16: error: Unsupported type "dict[str, object]" for ** expansion in TypedDict [typeddict-item]
Found 1 error in 1 file (checked 1 source file)
Your Environment
user@pc:~/$ mypy --version
mypy 1.8.0 (compiled: yes)
user@pc:~/$ python3 --version
Python 3.12.0
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
Reproduce the reported diagnostic from the provided main.py example with mypy 1.8.0 and inspect how TypedDict constructors handle ** expansion. No source file or test is named; done requires either a clear explanation of the restriction or a precisely scoped correction with regression coverage.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- devtools
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 35/100