Python Language Tutorial => Parsing Parentheses

Example

Stacks are often used for parsing. A simple parsing task is to check whether a string of parentheses are matching.

For example, the string ([]) is matching, because the outer and inner brackets form pairs. ()<>) is not matching, because the last ) has no partner. ([)] is also not matching, because pairs must be either entirely inside or outside other pairs.

def checkParenth(str):
    stack = Stack()
    pushChars, popChars = "<({[", ">)}]"
    for c in str:
        if c in pushChars:
            stack.push(c)
        elif c in popChars:
            if stack.isEmpty():
                return False
            else:
                stackTop = stack.pop()
                # Checks to see whether the opening bracket matches the closing one
                balancingBracket = pushChars[popChars.index(c)]
                if stackTop != balancingBracket:
                    return False
        else:
            return False

    return not stack.isEmpty()

PDF - Download Python Language for free

Previous Next

Python Language

Fastest Entity Framework Extensions

Example

Got any Python Language Question?

Python Language

Python Language Stack Parsing Parentheses

Fastest Entity Framework Extensions

Example

Got any Python Language Question?