Python - Attribute Error error I can't figure out - 'str' object has no attribute &#0-CodePudding

I'm trying to make a set of functions that will implement a caesar cipher by defining new classes, within which is the actual code for the cipher. trying to run it gives me an attribute error:

original = self.get_message_text()

AttributeError: 'str' object has no attribute 'get_message_text'

Full code is posted below.

import string

class Message(object):

    def __init__(self, text):

        self.message_text = text
        #self.valid_words = load_words(WORDLIST_FILENAME) - commented out bc irrelevant here


    def get_message_text(self):
        '''
        Used to safely access self.message_text outside of the class
    
        Returns: self.message_text
        '''
        return self.message_text

    def build_shift_dict(self, shift):
        letters_lower, letters_upper = string.ascii_lowercase, string.ascii_uppercase
    
    
        new_dict={}
        for letter in letters_upper:
            new_dict[letter] = letters_upper[(letters_upper.index(letter)   shift) % 26]
        for letter in letters_lower:
            new_dict[letter] = letters_lower[(letters_lower.index(letter)   shift) % 26]
    
        return new_dict

    def apply_shift(self, shift):
    
        original = self.get_message_text()
        new = ''
        for letter in original:
            new  = (self.build_shift_dict(shift))
        
        #print(new) - a test print
        return new

print(Message.apply_shift('tweLve',12))

disclaimer: this is a part of the MIT edx python course but I've checked through all of their notes & forum posts and I am none the wiser. Any help would be appreciated

EDIT: full error message, also I forgot to add the final print statement in the code

Traceback (most recent call last):

File ~.spyder-py3\ps5.py:239 in print(Message.apply_shift('tweLve',12))

File ~.spyder-py3\ps5.py:129 in apply_shift original = self.get_message_text()

AttributeError: 'str' object has no attribute 'get_message_text'

CodePudding user response：

You have to initiate the class object before running its functions

Full code:

import string


class Message(object):

    def __init__(self, text):

        self.message_text = text
        # self.valid_words = load_words(WORDLIST_FILENAME) - commented out bc irrelevant here

    def get_message_text(self):
        '''
        Used to safely access self.message_text outside of the class

        Returns: self.message_text
        '''
        return self.message_text

    def build_shift_dict(self, shift):
        letters_lower, letters_upper = string.ascii_lowercase, string.ascii_uppercase

        new_dict = {}
        for letter in letters_upper:
            new_dict[letter] = letters_upper[(letters_upper.index(letter)   shift) % 26]
        for letter in letters_lower:
            new_dict[letter] = letters_lower[(letters_lower.index(letter)   shift) % 26]

        return new_dict

    def apply_shift(self, shift):

        original = self.get_message_text()
        new = ''
        for letter in original:
            new  = (self.build_shift_dict(shift))

        # print(new) - a test print
        return new


if __name__ == '__init__':
    class_obj = Message(text='foo')
    original = class_obj.get_message_text()
    print(original)

CodePudding user response：

You should create instance of class and use this instance with apply_shift()

item = Message("tweLve") 
print( item.apply_shift(12) )