According to PEP479, the raise of StopIteration to end the loop of a generator may lead to hard to find bugs. This PEP specifies that raise StopIteration has to be replaced by a simple return statement.

Bad practice

def some_generator(n):
    for i in range(n):
        yield i
        if i >= 5:
            raise StopIteration  # Will raise an exception

Recommended

def some_generator(n):
    for i in range(n):
        yield i
        if i >= 5:
            return  # Will close the generator