Python Generators
Overview
Python generators are a type of iterator in Python, with the important caviat that you can only iterate over them once.
They are created by writing a function what uses the keyword yield
rather than return
.
Type Annotations
Generators can be annotated with the Generator
type that is defined in the typing
module:
Generator[yield_type, send_type, return_type]
Code Examples
The following code example chunks up a list:
def chunkify(l: List[Any], n: int) -> Generator[List[Any], None, None]: """ Provides a generator which provides chunks of size n of the list.
Args: l: The list to chunk up. n: The number of list elements to include in each chunk. Each chunk will be of length n, except for the last chunk, which may be from 1 to length n depending on the number of remaining elements.
Returns: A generator which, when iterated over, provides the chunks. """
for i in range(0, len(l), n): # Make sure we don't go over the bounds of the iterable on the last chunk upper_bound = min(i + n, len(l)) yield l[i : upper_bound]