it convert infix notation to postfix

Author: raianmol172

infix_to_postfix.py

@@ -0,0 +1,75 @@
+class Stack:
+    precedence = {'^': 5, '*': 4, '/': 4, '-': 3, '+': 3, '(': 2, ')': 1}
+
+    def __init__(self):
+        self.items = []
+        self.size = -1
+
+    def push(self, value):
+        self.items.append(value)
+        self.size += 1
+
+    def isEmpty(self):
+        return self.items == []
+
+    def pop(self):
+        if self.isEmpty():
+            return 0
+        else:
+            self.size -= 1
+            return self.items.pop()
+
+    def seek(self):
+        if self.isEmpty():
+            return False
+        else:
+            return self.items[self.size]
+
+    def isOperand(self, i):
+        if i in "ABCDEFGHIJKLMNOPQRSTUVWXYZ":
+            return True
+        else:
+            return False
+
+    def infix_to_postfix(self, expr):
+        postfix = ""
+
+        for i in expr:
+            if len(expr) % 2 == 0:
+                print("Invalid Expression")
+                return False
+
+            elif self.isOperand(i):
+                postfix += i
+
+            elif i in '^*+-/':
+                while len(self.items) and self.precedence[i] <= self.precedence[self.seek()]:
+                    postfix += self.pop()
+
+                self.push(i)
+
+            elif i in '(':
+                self.push(i)
+
+            elif i in ')':
+                temp = self.pop()
+                while temp != '(':
+                    postfix += temp
+                    temp = self.pop()
+            print(postfix)
+        while len(self.items):
+            if self.seek() == '(':
+                self.pop()
+
+            else:
+                postfix += self.pop()
+        return postfix
+
+
+s = Stack()
+expr = "(A+B)*C"
+result = s.infix_to_postfix(expr)
+if result != False:
+    print("the postfix of :", expr,  "is", result)
+
+