is it considered good practice to ...

[nilamo]

You can't use annotations with lambdas, if that matters to you.

>>> def outer():
...   def inner(n: int) -> int:
...     return n ** 2
...   return inner
...
>>> x = outer()
>>> x(4)
16
>>> def outer_lamb():
...   return lambda n: int -> int: n ** 2
 File "<stdin>", line 2
   return lambda n: int -> int: n ** 2
                         ^
SyntaxError: invalid syntax