python - AttributeError: 'str' object has no attribute 'build_shift_dict'? -
i solving quiz requires write code generate ciphered text, depends on simple algorithm shift characters number of steps toward right. here code , don't know error, i'm trying find 'str' in code can't find ever !! can tell me wrong code , how fix run ?
import string ### not modify function ### def load_words(file_name): ''' file_name (string): name of file containing list of words load returns: list of valid words. words strings of lowercase letters. depending on size of word list, function may take while finish. ''' print('loading word list 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 ### not modify function ### def is_word(word_list, word): ''' determines if word valid word, ignoring capitalization , punctuation word_list (list): list of words in dictionary. word (string): possible word. returns: true if word 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 ### not modify function ### def get_story_string(): """ returns: joke in encrypted text. """ f = open("story.txt", "r") story = str(f.read()) f.close() return story wordlist_filename = 'words.txt' class message(object): ### not modify method ### def __init__(self, text): ''' initializes message object text (string): message's text message object has 2 attributes: self.message_text (string, determined input text) self.valid_words (list, determined using helper function load_words ''' self.message_text = text self.valid_words = load_words(wordlist_filename) ### not modify method ### def get_message_text(self): ''' used safely access self.message_text outside of class returns: self.message_text ''' return self.message_text ### not modify method ### def get_valid_words(self): ''' used safely access copy of self.valid_words outside of class returns: copy of self.valid_words ''' return self.valid_words[:] def build_shift_dict(shift): ''' creates dictionary can used apply cipher letter. dictionary maps every uppercase , lowercase letter character shifted down alphabet input shift. dictionary should have 52 keys of uppercase letters , lowercase letters only. shift (integer): amount shift every letter of alphabet. 0 <= shift < 26 returns: dictionary mapping letter (string) letter (string). ''' assert 0 <= shift < 26 shifted_dict = {} def shift_letters(shift, text): in range(len(text)): if < shift: shifted_dict[text[i]] = text[26 - shift + i] else: shifted_dict[text[i]] = text[i - shift] shift_letters(shift, string.ascii_lowercase) shift_letters(shift, string.ascii_uppercase) return shifted_dict def apply_shift(self, shift): ''' applies caesar cipher self.message_text input shift. creates new string self.message_text shifted down alphabet number of characters determined input shift shift (integer): shift encrypt message. 0 <= shift < 26 returns: message text (string) in every character shifted down alphabet input shift ''' shifted_dict = self.build_shift_dict(shift) result = "" in self.message_text: if not in string.ascii_lowercase , not in string.ascii_uppercase: result += else: result += shifted_dict[i] return result class plaintextmessage(message): def __init__(self, text, shift): ''' initializes plaintextmessage object text (string): message's text shift (integer): shift associated message plaintextmessage object inherits message , has 5 attributes: self.message_text (string, determined input text) self.valid_words (list, determined using helper function load_words) self.shift (integer, determined input shift) self.encrypting_dict (dictionary, built using shift) self.message_text_encrypted (string, created using shift) hint: consider using parent class constructor less code repeated ''' self.text = text self.shift = shift self.encrypting_dict = message.build_shift_dict(shift) self.message_text_encrypted = message.apply_shift(text, shift) def get_shift(self): ''' used safely access self.shift outside of class returns: self.shift ''' return self.shift def get_encrypting_dict(self): ''' used safely access copy self.encrypting_dict outside of class returns: copy of self.encrypting_dict ''' return self.encrypting_dict def get_message_text_encrypted(self): ''' used safely access self.message_text_encrypted outside of class returns: self.message_text_encrypted ''' return self.message_text_encrypted() def change_shift(self, shift): ''' changes self.shift of plaintextmessage , updates other attributes determined shift (ie. self.encrypting_dict , message_text_encrypted). shift (integer): new shift should associated message. 0 <= shift < 26 returns: nothing ''' assert 0 <= shift < 26 self.shift = shift self.encrypting_dict = message.build_shift_dict(shift) self.message_text_encrypted = message.apply_shift(text, shift) class ciphertextmessage(message): def __init__(self, text): ''' initializes ciphertextmessage object text (string): message's text ciphertextmessage object has 2 attributes: self.message_text (string, determined input text) self.valid_words (list, determined using helper function load_words) ''' self.message = message def decrypt_message(self): ''' decrypt self.message_text trying every possible shift value , find "best" one. define "best" shift creates maximum number of real words when use apply_shift(shift) on message text. if s original shift value used encrypt message, expect 26 - s best shift value decrypting it. note: if multiple shifts equally such create maximum number of may choose of shifts (and corresponding decrypted messages) return returns: tuple of best shift value used decrypt message , decrypted message text using shift value ''' in range(26): decrypted = message.apply_shift(self.message , i) word in decrypted : if word in message.valid_words : return (i , decrypted) # 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()) i wrote every time run code gives me error !!??
traceback (most recent call last): file "c:/users/ahmad galal/desktop/ps6/ps6.py", line 248, in <module> plaintext = plaintextmessage('hello', 2) file "c:/users/ahmad galal/desktop/ps6/ps6.py", line 168, in __init__ self.message_text_encrypted = message.apply_shift(text, shift) file "c:/users/ahmad galal/desktop/ps6/ps6.py", line 137, in apply_shift shifted_dict = eval(self.build_shift_dict(shift)) attributeerror: 'str' object has no attribute 'build_shift_dict' process finished exit code 1
def build_shift_dict(shift) means message instance not have build_shift_dict.
change def build_shift_dict(shift) def build_shift_dict(self, shift)
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