Added infix to postfix program

Infix to Postfix.py

@@ -0,0 +1,63 @@
+'''
+Given an infix expression convert to postfix expression.
+Example Input:
+
+2+3*7-9/5
+
+Output:
+
+237*+95/-
+'''
+
+class Fixes:
+    def __init__(self,s):
+        self.s=s
+    def prec(self,ch):
+        if(ch=='+' or ch=='-'):
+            return 1
+        elif(ch=='*' or ch=='/'):
+            return 2
+        else:
+            return 3
+    def convert(self):
+        stack=[]
+        top=-1
+        ans=[]
+        n=len(self.s)
+        for i in range(n):
+            if(self.s[i].isdigit()):
+                ans.append(self.s[i])
+            elif(self.s[i]=='('):
+                stack.append(self.s[i])
+                top+=1
+            elif(self.s[i]==')'):
+                while(top>-1 and stack[top]!='('):
+                    ans.append(stack.pop())
+                    top-=1
+                if(stack[top]=='('):
+                    stack.pop()
+                    top-=1
+            else:
+                while top>-1 and stack[top]!='(' and self.prec(self.s[i])<=self.prec(stack[top]):
+                        ans.append(stack.pop())
+                        top-=1
+                stack.append(self.s[i])
+                top+=1
+
+        while(top>-1):
+            ans.append(stack.pop())
+            top-=1
+        s=''
+        for i in ans:
+            if i!='\r':
+                s+=i
+        self.postfix=s
+
+testcases = int(input())
+for _ in range(testcases):
+    equation = input()
+    fix = Fixes(equation)
+    print(f'Infix: {equation}')
+    fix.convert()
+    print(f'Postfix: {fix.postfix}')
+    print('---')