Arithmetic Progression with a Closure, and a Generator

arithmetic-progression.py

def arith(a: 'initial term', d: 'common difference'):
    """Returns initial and subsequent arithmetic progression terms"""
    current = a - d

    def _():
        nonlocal current
        current += d
        return current
    return _


def arith_gen(a, d):
    """Same function as above except it uses generators"""
    current = a
    while True:
        yield current
        current += d


if __name__ == '__main__':
    a = arith(1, 2)
    print(a())
    print(a())
    print(a())

    a = arith_gen(1, 2)
    print(next(a))
    print(next(a))
    print(next(a))