I have a type for a dictionary of variables passed to a template:
VariablesDict = Dict[str, Union[int, float, str, None]]Basically, any dictionary where the keys are strings and the values are strings, numbers or None. I use this type in several template related functions.
Take this example function:
def render_template(name: str, variables: VariablesDict): ...Calling this function with a dictionary literal works fine:
render_template("foo", {"key": "value"})However, if I assign the dictionary to a variable first, like this:
variables = {"key": "value"}render_template("foo", variables)Mypy gives an error:
Argument 2 to "render_template" has incompatible type "Dict[str, str]"; expected "Dict[str, Union[int, float, str, None]]"
It seems to me that any value of type Dict[str, str] should be safe to pass to a function that expects a parameter of type Dict[str, Union[int, float, str, None]]. Why doesn't that work by default? Is there anything I can do to make this work?