Valid Parentheses

def valid_parentheses(expression):
    stack = []

    for symbol in expression:
        if symbol in ['(', '[', '{']:
            stack.append(symbol)

        # if the previous parentheses is a match, then pop that match
        elif stack and (
            (symbol == ')' and stack[-1] == '(') or\
            (symbol == ']' and stack[-1] == '[') or\
            (symbol == '}' and stack[-1] == '{')):
            stack.pop()

    # the stack would be empty if all the parentheses match
    return not stack