Infix to postfix in Python

Added program for Infix to Postfix in Python

Python/InfixToPostfix.py

@@ -0,0 +1,70 @@
+
+class SampleProgram : 
+
+    def __init__(self, capacity): 
+        self.top = -1 
+        self.capacity = capacity 
+        self.array = [] 
+        self.output = [] 
+        self.precedence = {'+':1, '-':1, '*':2, '/':2, '^':3} 
+
+    def isEmpty(self): 
+        return True if self.top == -1 else False
+
+    def peek(self): 
+        return self.array[-1] 
+
+    def pop(self): 
+        if not self.isEmpty(): 
+            self.top -= 1
+            return self.array.pop() 
+        else: 
+            return "$"
+
+    def push(self, op): 
+        self.top += 1
+        self.array.append(op)  
+
+    def isOperand(self, ch): 
+        return ch.isalpha() 
+
+    def notGreater(self, i): 
+        try: 
+            a = self.precedence[i] 
+            b = self.precedence[self.peek()] 
+            return True if a  <= b else False
+        except KeyError:  
+            return False
+
+
+    def InfixToPostfix(self, exp): 
+
+        for i in exp: 
+            if self.isOperand(i): 
+                self.output.append(i) 
+
+            elif i  == '(': 
+                self.push(i) 
+
+            elif i == ')': 
+                while( (not self.isEmpty()) and self.peek() != '('): 
+                    a = self.pop() 
+                    self.output.append(a) 
+                if (not self.isEmpty() and self.peek() != '('): 
+                    return -1
+                else: 
+                    self.pop() 
+
+            else: 
+                while(not self.isEmpty() and self.notGreater(i)): 
+                    self.output.append(self.pop()) 
+                self.push(i) 
+
+        while not self.isEmpty(): 
+            self.output.append(self.pop()) 
+
+        print "".join(self.output) 
+
+exp = "a+b*(c^d-e)^(f+g*h)-i"
+obj = SampleProgram(len(exp)) 
+obj.InfixToPostfix(exp)