In Python 3.8 and later, the approach suggested by MSeifert and Richard Xia can be improved by not using the undocumented attributes __origin__ and __args__. This functionality is provided by the new functions typing.get_args(tp) and typing.get_origin(tp): >> from typing import Union, get_origin, get_args >> x = Union[int, str] >> get_origin(x), get_args(x) (typing.Union, (<class ‘int’>, <class … Read more
Yes it is possible you are very close, you can use the predefined Extract conditional type. You can will need to pass in, as the second argument, a type that can be a base type for the type you are seeking: type LinkItem = Extract<Item, { type: ‘link’ }> // will be { type: “link”; … Read more
T‘s type must be consistent across multiple uses within a given scope, while U‘s does not. With a Union type used as function parameters, the arguments as well as the return type can all be different: U = Union[int, str] def union_f(arg1: U, arg2: U) -> U: return arg1 x = union_f(1, “b”) # No … Read more
DISCLAIMER: DON’T DO THIS!! If someone tells you to use the code they found in this answer to do anything except demonstrate why this is a bad idea, RUN AWAY!! It’s easy to convert from a tuple type to a union type; for example, see this question. But the opposite, converting from a union to … Read more
To get the type of a variable you need to use the typeof type operator: const MY_CONSTANT = ‘MY_CONSTANT’ // must be const, no annotation. let or var will not work const SOMETHING_ELSE = ‘SOMETHING_ELSE’ // must be const, no annotation. let or var will not work type MyType = typeof MY_CONSTANT | typeof SOMETHING_ELSE … Read more
Edit for 4.2 map has become callable now, but you still need an explicit type annotation on its argument to get it to work as expected (the type parameter is no contextually typed) let test: Test1[] | Test2[] = []; test.map((obj: Test1 | Test2) => {}); Playground Link This situation is likely to improve in … Read more
Use float only, as int is implied in that type: def my_func(number: float): PEP 484 Type Hints specifically states that: Rather than requiring that users write import numbers and then use numbers.Float etc., this PEP proposes a straightforward shortcut that is almost as effective: when an argument is annotated as having type float, an argument … Read more
To understand the keyof typeof usage in TypeScript, first you need to understand what are literal types and union of literal types. So, I’ll explain these concepts first and then explain keyof and typeof individually in detail. After that, I’ll come back to enum to answer what is asked in the question. It’s a long … Read more