def parenthesis(string):
    openchr = { 
        '(' : 0,
        '{' : 1,
        '[' : 2
    }
    closechr = { 
        ')' : 0,
        '}' : 1,
        ']' : 2
    }
    visited = []
    
    for char in string:
        if char in openchr:
            visited.append(char)
        else:
            if len(visited) == 0:
                return False
            popped = visited.pop(-1)
            if (openchr[popped] != closechr[char]):
                return False

    if len(visited) == 0:
        return True
    return False