Let's check if a given parenthesis string is in a valid form.

expanded_parenthesis.py

def is_right_parenthesis(parens):
    OPENERS = '([{'
    CLOSERS = ')]}'
    MAP = dict(zip(CLOSERS, OPENERS)) # {  ')': '(', ']': '[', '}': '{'  } 와 동일
    stack = []
    
    for p in parens:
        if p in OPENERS:
            stack.append(p)
        else:
            if not stack:
                return False
            opener = stack.pop()
            if opener != MAP[p]:
                return False

    return not stack