def is_paired(input_string): stack = [] for char in input_string: if char == '(' or char == '[]' or char == '{': stack.append(char) elif char == ')': if len(stack) == 0 or stack.pop() != '(': return False elif char == ']': if len(stack) == 0 or stack.pop() != '[': return False elif char == '}': if len(stack) == 0 or stack.pop() != '{': return False return len(stack) == 0