parens.py

#!/usr/bin/env python3

"Generate all strings containing just ( and ) with parens balenced."

from itertools import count

def parens():
    def nested(x):
        return ("(" * x) + (")" * x) if x > 0 else ""

    def n_parens(n):
        yield nested(n)
        yield from (nested(i) + p for i in range(1, n) for p in n_parens(n - i))

    return (x for n in count() for x in n_parens(n))


if __name__ == "__main__":

    for i, p in enumerate(parens()):
        print(p)
        if i > 100:
            break