Postfix-Expressions-in-python/Stack.py at Main · MahaLakshmi729/Postfix-Expressions-in-python · GitHub

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class Stack:
    def __init__(self) -> None:
        self.stack=[]
        self.top=-1

    def push(self,val):
        if len(self.stack)==0:
            self.stack.append(val)
            self.top+=1

        else:
            self.stack.append(val)
            self.top+=1

    def show_top(self):
        if len(self.stack)>0:
            return self.stack[self.top]
        return None

    def pop(self):
        if len(self.stack) > 0:
            self.top -=1
            return self.stack.pop()
        return None

    def show(self):
        print(self.stack)

    def is_empty(self):
        if len(self.stack) == 0:
            return True
        return False

    def exists(self,val):
        return (val in self.stack)