python typing optional

1from typing import Optional
2
3class Example:
4  required_field_1: str
5  required_field_2: int
6  optional_field: Optional[str]

1from typing import List
2
3def my_func(l: List[int]):
4    pass
5

1# Iterator
2def infinite_stream(start: int) -> Iterator[int]:
3    while True:
4        yield start
5        start += 1
6
7# Generator        
8def infinite_stream(start: int) -> Generator[int, None, None]:
9    while True:
10        yield start
11        start += 1
12

1# For collections, the name of the type is capitalized, and the
2# name of the type inside the collection is in brackets
3x: List[int] = [1]
4x: Set[int] = {6, 7}
5  
6# For simple built-in types, just use the name of the type
7x: int = 1
8x: float = 1.0
9x: bool = True
10x: str = "test"
11x: bytes = b"test"