Transcript CS1315: Introduction to Media Computation

String
 X=“Python Rocks!”
 X.index(“O”)
Character Encoding
 ASCII code
 A – 65; B – 66; … ; Z – 90
 http://www.asciitable.com/
 >>> ord(‘A’) # ASCII value or order of letter
 >>> chr(65) # opposite of ord()
Cryptography
 Encoding and Decoding Messages
Translation Cipher
 Replace each character by ord(character)+constant

A B C D E F ….

0 1 2 3 4 5 ….
 +5
5 6 7 8 9 10 …
 26 or over -> wrap around
X Y Z
23 24 25
EncoderDecoder
# Ask what message you want to encrypt, and name it ‘msg’
msg = msg.upper()
# make all uppercases
# Initially, set ‘cipher’ is blank
for letter in msg:
# get the order of the letter and add 5
# find a char for the new order, but wrap around 26
# concatenate the new char to cipher
print(“Cipher text: “, cipher)
Cipher.py
# Ask what message you want to encrypt, and name it ‘msg’
msg = msg.upper()
# make all uppercases
# Initially, set ‘cipher’ is blank
for letter in msg:
# get the order of the letter and add 5
# find a char for the new order, but wrap around 26
# concatenate the new char to cipher
print(“Cipher text: “, cipher)
EncoderDecoder.py (p.99)
message = input(“Enter a message to encrypt: \n”)
message = message.upper()
cipher = “”
for letter in message:
if letter.isupper():
val = ord(letter)+13
newlet = chr(val)
if not newlet.isupper():
newlet = chr(val-26)
cipher = cipher + newlet
print(“Cipher text: “, cipher)
Update with Modulo Function
message = input(“Enter a
message to encode: \n”)
message = input(“Enter a message to
encode: \n”)
message = message.upper()
message = message.upper()
cipher = “”
cipher = “”
for letter in message:
for letter in message:
if letter.isupper():
val = ord(letter)+13
newlet = chr(val)
if not newlet.isupper():
newlet = chr(val-26)
cipher = cipher + newlet
print(“Cipher text: “, cipher)
cipher = cipher + newlet
print(“Cipher text: “, cipher)
Encryption Key
Vigenere Square
Eliza
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A word game to simulate Gestalt psychotherapist
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Hello. Welcome to therapy. What is your name ? Tim
Well Tim, What can we do for you today? I am writing
a book on Python
Tell me more. Do you know Python?
Why do you want to know?
Eliza
Lab_0226
 Modify Eliza program
 Add the main (control) program that repeated ask
for your response and call function runEliza()
 Add at least one ‘elif’ case
 Add more cases to handle
 Email to [email protected]