Adding the encrypt.py main script using some functions in the translate.py script for the rot13 assignment.

imdavis · imdavis · commit 0c29f344dff2 · 2014-10-19T22:32:55.000-07:00
diff --git a/Students/imdavis/session03/rot13/encrypt.py b/Students/imdavis/session03/rot13/encrypt.py
@@ -0,0 +1,9 @@
+#!/usr/bin/env python2.7
+
+from translate import rot13
+
+astring = raw_input("Enter a string to encrypt > ")
+encrypted_string = rot13(astring)
+
+print "Original string:", astring
+print "Encrypted string:", encrypted_string
diff --git a/Students/imdavis/session03/rot13/translate.py b/Students/imdavis/session03/rot13/translate.py
@@ -0,0 +1,70 @@
+#!/usr/bin/env python2.7
+# -*- coding: utf-8 -*-
+
+"""
+    Some functions to create a basic substitution cypher.
+    Any letter in the alphabet is replaced with the letter 13 spaces away
+    The 'rotation' variable can be modified to set the rotation to something
+    other than 13. A rotation of 13 makes it such that, you can encrypt and 
+    decrypt using these functions, since there are 26 letters in the alphabet.
+    This is designed to leave whitespace, punctuation, and capitalization 
+    intact in the encrypted string as in the original.
+
+    Lowercase a-z are ordinals 197 -122 (enclusive)
+    For example: ord('s') = 115 and chr(115) = 's'
+
+"""
+
+def lowercase(substring):
+    """
+    Convert a string to lower case so that we only have to deal with 
+    the ordinal values for the lowercase letters.
+    """
+    if(substring.islower()):
+        alower = True
+    else:
+        alower = False
+        substring = substring.lower()
+    return alower, substring
+
+def encrpt_letter(substring, rot):
+    """
+    Find the ordinal of the encrypted letter
+    """
+    letter_pos = ord(substring) + rot
+    if(letter_pos > 122):
+        letter_pos = 97 + (letter_pos%122 - 1)
+    return chr(letter_pos)
+
+def rot13(user_string):
+    """
+    Take the user string and create the encrypted string
+    """
+    cipher_string = ""
+    rotation=13
+    atoz_range = range(97, 123)
+    for aletter in user_string:
+        lower, aletter = lowercase(aletter)
+        if( ord(aletter) in atoz_range):
+            cipher_letter = encrpt_letter(aletter, rotation)
+            if(not lower):
+                cipher_letter = cipher_letter.swapcase()
+        else:
+            cipher_letter = aletter
+        cipher_string += cipher_letter
+    return cipher_string
+
+# Some basic testing 
+if __name__ == '__main__':
+    teststring1 = "Magnetic from outside near corner"
+    teststring2 = "Zntargvp sebz bhgfvqr arne pbeare"
+    teststring3 = "A string of some stuff with SOME CAPS and numbers 1, 4, 75, etc. ?#$, yeah!"
+    teststring4 = "N fgevat bs fbzr fghss jvgu FBZR PNCF naq ahzoref 1, 4, 75, rgp. ?#$, lrnu!"
+    try:
+        assert rot13(teststring1) == teststring2
+        assert rot13(teststring2) == teststring1
+        assert rot13(teststring3) == teststring4
+        assert rot13(teststring4) == teststring3
+
+    except AssertionError:
+        print "Tests did not pass!"
