'''

def __init__(self, limit = 10):

'''

self.stack = []

self.limit = limit

# for printing the stack contents

def __str__(self):

return ' '.join([str(i) for i in self.stack])

# for pushing an element on to the stack

def push(self, data):

if len(self.stack) >= self.limit:

return -1 # indicates stack overflow

else:

self.stack.append(data)

# for popping the uppermost element

def pop(self):

if len(self.stack) <= 0:

return -1 # indicates stack underflow

else:

return self.stack.pop()

# for peeking the top-most element of the stack

def peek(self):

if len(self.stack) <= 0:

return -1 # stack underflow

else:

return self.stack[len(self.stack) - 1]

# to check if stack is empty

def isEmpty(self):

return self.stack == []

# for checking the size of stack

def size(self):

return len(self.stack)

# easily retrieve the source code of the Stack class

def get_code(self):

import inspect

'''

def __init__(self, expression = [], stack = None):

'''

self.myExp = list(expression)

self.myStack = stack

# function to check whether the given character of the expression is operand

def _isOperand(self, char):

return (ord(char) >= ord('a') and ord(char) <= ord('z')) or (ord(char) >= ord('A') and ord(char) <= ord('Z'))

# self defined precedence for each operator

def _precedence(self, char):

if char == '+' or char == '-':

return 1

elif char == '*' or char == '/':

return 2

elif char == '^':

return 3

else:

return -1

# function to convert infix to postfix

def infix_to_postfix(self):

postFix = []

for i in range(len(self.myExp)):

if (self._isOperand(self.myExp[i])):

postFix.append(self.myExp[i])

elif(self.myExp[i] == '('):

self.myStack.push(self.myExp[i])

elif(self.myExp[i] == ')'):

topOperator = self.myStack.pop()

while(not self.myStack.isEmpty() and topOperator != '('):

postFix.append(topOperator)

topOperator = self.myStack.pop()

else:

while (not self.myStack.isEmpty()) and (self._precedence(self.myExp[i]) <= self._precedence(self.myStack.peek())):

postFix.append(self.myStack.pop())

self.myStack.push(self.myExp[i])

while(not self.myStack.isEmpty()):

postFix.append(self.myStack.pop())

return ' '.join(postFix)

# easily retrieve the source code of the Stack class

def get_code(self):

import inspect