Add Chapter 9 exercises

thinkcspy/Chapter-9-Exercises/Python-files/Problem18.py

@@ -0,0 +1,24 @@
+# Runestone.Academy thinkcspy course
+# Chapter 9
+# Problem 18
+
+import string
+
+def encrypt(msg, code):
+    alpha = string.ascii_lowercase
+    newStr = ""
+    pos = 0
+    msg = msg.lower()
+    
+    for char in msg:
+        if char in alpha:
+            pos = alpha.index(char)
+            newStr += newAlpha[pos]
+        else:
+            newStr += char    # no rules apply so keep the character
+
+    return newStr
+
+newAlpha = "qwertyuiopasdfghjklzxcvbnm"
+
+print(encrypt("Hello World!", newAlpha))