import string
### DO NOT MODIFY THIS FUNCTION ###
def load_words(file_name):
'''
file_name (string): the name of the file containing
the list of words to load
Returns: a list of valid words. Words are strings of lowercase letters.
Depending on the size of the word list, this function may
take a while to finish.
'''
print('Loading word list from file...')
# inFile: file
in_file = open(file_name, 'r')
# line: string
line = in_file.readline()
# word_list: list of strings
word_list = line.split()
print(' ', len(word_list), 'words loaded.')
in_file.close()
return word_list
### DO NOT MODIFY THIS FUNCTION ###
def is_word(word_list, word):
'''
Determines if word is a valid word, ignoring
capitalization and punctuation
word_list (list): list of words in the dictionary.
word (string): a possible word.
Returns: True if word is in word_list, False otherwise
Example:
>>> is_word(word_list, 'bat') returns
True
>>> is_word(word_list, 'asdf') returns
False
'''
word = word.lower()
word = word.strip(" !@#$%^&*()-_+={}[]|\:;'<>?,./\"")
return word in word_list
### DO NOT MODIFY THIS FUNCTION ###
def get_story_string():
"""
Returns: a joke in encrypted text.
"""
f = open("story.txt", "r")
story = str(f.read())
f.close()
return story
WORDLIST_FILENAME = 'words.txt'
class Message(object):
### DO NOT MODIFY THIS METHOD ###
def __init__(self, text):
'''
Initializes a Message object
text (string): the message's text
a Message object has two attributes:
self.message_text (string, determined by input text)
self.valid_words (list, determined using helper function load_words
'''
self.message_text = text
self.valid_words = load_words(WORDLIST_FILENAME)
### DO NOT MODIFY THIS METHOD ###
def get_message_text(self):
'''
Used to safely access self.message_text outside of the class
Returns: self.message_text
'''
return self.message_text
### DO NOT MODIFY THIS METHOD ###
def get_valid_words(self):
'''
Used to safely access a copy of self.valid_words outside of the class
Returns: a COPY of self.valid_words
'''
return self.valid_words[:]
def build_shift_dict(self, shift):
'''
Creates a dictionary that can be used to apply a cipher to a letter.
The dictionary maps every uppercase and lowercase letter to a
character shifted down the alphabet by the input shift. The dictionary
should have 52 keys of all the uppercase letters and all the lowercase
letters only.
shift (integer): the amount by which to shift every letter of the
alphabet. 0 <= shift < 26
Returns: a dictionary mapping a letter (string) to
another letter (string).
'''
pass #delete this line and replace with your code here
def apply_shift(self, shift):
'''
Applies the Caesar Cipher to self.message_text with the input shift.
Creates a new string that is self.message_text shifted down the
alphabet by some number of characters determined by the input shift
shift (integer): the shift with which to encrypt the message.
0 <= shift < 26
Returns: the message text (string) in which every character is shifted
down the alphabet by the input shift
'''
pass #delete this line and replace with your code here
class PlaintextMessage(Message):
def __init__(self, text, shift):
'''
Initializes a PlaintextMessage object
text (string): the message's text
shift (integer): the shift associated with this message
A PlaintextMessage object inherits from Message and has five attributes:
self.message_text (string, determined by input text)
self.valid_words (list, determined using helper function load_words)
self.shift (integer, determined by input shift)
self.encrypting_dict (dictionary, built using shift)
self.message_text_encrypted (string, created using shift)
Hint: consider using the parent class constructor so less
code is repeated
'''
pass #delete this line and replace with your code here
def get_shift(self):
'''
Used to safely access self.shift outside of the class
Returns: self.shift
'''
pass #delete this line and replace with your code here
def get_encrypting_dict(self):
'''
Used to safely access a copy self.encrypting_dict outside of the class
Returns: a COPY of self.encrypting_dict
'''
pass #delete this line and replace with your code here
def get_message_text_encrypted(self):
'''
Used to safely access self.message_text_encrypted outside of the class
Returns: self.message_text_encrypted
'''
pass #delete this line and replace with your code here
def change_shift(self, shift):
'''
Changes self.shift of the PlaintextMessage and updates other
attributes determined by shift (ie. self.encrypting_dict and
message_text_encrypted).
shift (integer): the new shift that should be associated with this message.
0 <= shift < 26
Returns: nothing
'''
pass #delete this line and replace with your code here
class CiphertextMessage(Message):
def __init__(self, text):
'''
Initializes a CiphertextMessage object
text (string): the message's text
a CiphertextMessage object has two attributes:
self.message_text (string, determined by input text)
self.valid_words (list, determined using helper function load_words)
'''
pass #delete this line and replace with your code here
def decrypt_message(self):
'''
Decrypt self.message_text by trying every possible shift value
and find the "best" one. We will define "best" as the shift that
creates the maximum number of real words when we use apply_shift(shift)
on the message text. If s is the original shift value used to encrypt
the message, then we would expect 26 - s to be the best shift value
for decrypting it.
Note: if multiple shifts are equally good such that they all create
the maximum number of you may choose any of those shifts (and their
corresponding decrypted messages) to return
Returns: a tuple of the best shift value used to decrypt the message
and the decrypted message text using that shift value
'''
pass #delete this line and replace with your code here
#Example test case (PlaintextMessage)
plaintext = PlaintextMessage('hello', 2)
print('Expected Output: jgnnq')
print('Actual Output:', plaintext.get_message_text_encrypted())
#Example test case (CiphertextMessage)
ciphertext = CiphertextMessage('jgnnq')
print('Expected Output:', (24, 'hello'))
print('Actual Output:', ciphertext.decrypt_message())