convert-typed-dict-functional-to-class (UP013)

Derived from the pyupgrade linter.

Fix is sometimes available.

What it does

Checks for TypedDict declarations that use functional syntax.

Why is this bad?

TypedDict types can be defined either through a functional syntax (Foo = TypedDict(...)) or a class syntax (class Foo(TypedDict): ...).

The class syntax is more readable and generally preferred over the functional syntax.

Nonetheless, there are some situations in which it is impossible to use the class-based syntax. This rule will not apply to those cases. Namely, it is impossible to use the class-based syntax if any TypedDict fields are:

• Not valid python identifiers (for example, @x)
• Python keywords such as in
• Private names such as __id that would undergo name mangling at runtime if the class-based syntax was used
• Dunder names such as __int__ that can confuse type checkers if they're used with the class-based syntax.

Example

from typing import TypedDict

Foo = TypedDict("Foo", {"a": int, "b": str})

Use instead:

from typing import TypedDict


class Foo(TypedDict):
    a: int
    b: str

Fix safety

This rule's fix is marked as unsafe if there are any comments within the range of the TypedDict definition, as these will be dropped by the autofix.

References

• Python documentation: typing.TypedDict