python function type of argument code example

Example 1: python function argument type

def pick(l: list, index: int) -> int:
    return l[index]

Example 2: type declaration python

def greeting(name: str) -> str:
    return 'Hello ' + name

Example 3: python optional type annotation

from custom_module import SomeClass
from typing import Optional

class SubClass:
    a_reference: Optional[SomeClass] # Provides info that a_reference may be 'None'.

    def __init__(self):
        self.a_reference = None