I have a function that takes in a lambda:
def my_function(some_lambda):
# do stuff
some_other_variable = some_lambda(some_variable)
my_function(lambda x: x + 2)
I would like to typehint the lambda function passed.
I've tried
def my_function(some_lambda: lambda) -> None:
# SyntaxError: invalid syntax
from typing import Lambda
# ImportError: cannot import name 'Lambda'
My IDE complains about similar things on 2.7 straddled typehints, eg
def my_function(some_lambda: lambda) -> None:
# type: (lambda) -> None
# formal parameter name expected
This is obvious when you think about it, but it took a while to register in the head. A lambda is a function. There is no function type but there is a Callable type in the typing package. The solution to this problem is
from typing import Callable
def my_function(some_lambda: Callable) -> None:
Python 2 version:
from typing import Callable
def my_function(some_lambda):
# type: (Callable) -> None