Your code doesn't work because the map function returns an iterator so as you didn't iterate over the object returned by map, the result.append function is never called.

The "just working" version of your code would be something like:

def foo() -> list[int]:  # Note that the type hint here is incorrect as you don't return anything
    result: list = []
    tuple(map(result.append, [x for x in range(10) if x % 2 == 0]))
    print(result)

But this is very unoptimized, the version I would write would use directly the list comprehension:

def foo():
    print([x for x in range(10) if x % 2 == 0])

Otherwise you could use a filter:

def foo():
    print(list(filter(lambda x: x % 2 == 0, range(10))))

For more information, please read this article: https://realpython.com/python-map-function/