Add "Simple Calculator" example

Signed-off-by: Ercan Ersoy <ercanersoy@ercanersoy.net>

Author: ercanersoy

README.md

@@ -8,4 +8,5 @@ Copyright (c) 2020 Ercan Ersoy
 
 * [Hello World](hello-world)
 * [User Input](user-input)
-* [Circle Calculator](circle-calculator)
+* [Circle Calculator](circle-calculator)
+* [Simple Calculator](simple-calculator)

simple-calculator/simple-calculator.py

@@ -0,0 +1,34 @@
+while True:
+    print("1. Addition")
+    print("2. Substraction")
+    print("3. Multiplication")
+    print("4. Division")
+    print("5. Exit")
+    choice = input("Your choice: ")
+    
+    if choice == "1":
+        first_addend = float(input("First addend: "))
+        second_addend = float(input("Second addend: "))
+        print("Result: ", end="")
+        print(first_addend + second_addend)
+    elif choice == "2":
+        first_subtrahend = float(input("First subtrahend: "))
+        second_subtrahend = float(input("Second subtrahend: "))
+        print("Result: ", end="")
+        print(first_subtrahend - second_subtrahend)
+    elif choice == "3":
+        multiplier = float(input("Multiplier: "))
+        multiplicand = float(input("Multiplicand: "))
+        print("Result: ", end="")
+        print(multiplier * multiplicand)
+    elif choice == "4":
+        dividend = float(input("Dividend: "))
+        divider = float(input("Divider: "))
+        print("Result: ", end="")
+        print(dividend / divider)
+    elif choice == "5":
+        break
+    else:
+        print("Wrong choice!")
+
+