CODEWITHSUNDEEP
pythonpython-3.xnamedtuplemypy
Jean-Francois T.
Jean-Francois T.

Reputation: 12950

How to ignore mypy errors when using NamedTuples with default values

I have been able to have mypy do a type check on NamedTuple and use default values for NamedTuple.

However, I always have an error raised by mypy when I use default value.

Here is my code (I use Python 3.6)

class TestResult(NamedTuple):
    """To store results of a given Test Case"""

    outcome: str
    duration: Optional[int]  # in seconds
    comment: Optional[str]
    msg: Optional[str]


TestResult.__new__.__defaults__ = (None,) * 3  # type: ignore  # Hack for Python < 3.7

When I do passed_tc = TestResult("Passed"), I have the following error message

error:Too few arguments for "TestResult"

Anyone got an idea on how to tell mypy we can have optional arguments and avoid this error?

Upvotes: 1

Views: 1475

Answers (1)

Michael0x2a
Michael0x2a

Reputation: 64278

Assign the values that need default values with the desired default values. For example:

from typing import NamedTuple, Optional

class Test(NamedTuple):
    foo: str
    bar: Optional[str] = None
    qux: int = 100

t = Test("foo")

I've tested that this works at runtime for both Python 3.6 and 3.7, and confirmed it type-checks as expected using mypy 0.641.

Upvotes: 3

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