Re: [Tutor] Stack problem usind Python2.6

[bob gailer]

On 7/21/2011 5:16 PM, David Merrick wrote:

##from stack import Stack

class Stack:
    def __init__(self):
        self.items =[]

    def isEmpty(self):
        return self.items ==[]

    def push(self,item):
        self.items.append(item)

    def pop(self,item):
        self.items.pop()

    def peek(self):
        return  self.items[len(self.items)-1]

    def size(self):
        return len(self.items)

def parChecker(symbolString):
    s = Stack()

    balanced = True
    index = 0
    while index < len(symbolString) and balanced:
        symbol = symbolString[index]
        if symbol in "([{":
            s.push(symbol)
        else:
            if s.isEmpty():
                balanced = False
            else:
                top = s.pop()
                if not matches(top,symbol):
                    balanced = False
        index+=1
        if balanced and  s.isEmpty():
            return True
        else:
            return False

def matches(open,close):
    opens = "([{"
    closers = ")]}"

    opens.index(open) == closers.index(close)

symbolString = "()"
print(parChecker(symbolString))

_*Output*_

() returns False should be true
(() returns False which is correct

I can't find the error please help me

What do you tkink matches returns, and why?

Therein is the problem.

Also FWIW you import Stack them redefine it. Why?


--
Bob Gailer
919-636-4239
Chapel Hill NC


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