return types in python 3 code example

Example 1: specify return type python function

def greeting(name: str) -> str:
  return 'Hello, {}'.format(name)

Example 2: typing generator python

# Iterator
def infinite_stream(start: int) -> Iterator[int]:
    while True:
        yield start
        start += 1

# Generator        
def infinite_stream(start: int) -> Generator[int, None, None]:
    while True:
        yield start
        start += 1