Encoding a string using function-CodePudding

I created the following function to pair each letter in the alphabet with its corresponding encoded letter based on a given shift:

alphabet = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']


def build_cipher(shift):
    '''
    Description: takes in shift (an integer representing the amount the letter key in the dictionary is shifted from its corresponding letter) and returns a dictionary containing all letters and their corresponding letters after the shift. This is achieved through subtracting the shift from the number corresponding to the letter, and using modulo 26.
    
    >>> build_cipher(-3)
    {'a': 'x', 'b': 'y', 'c': 'z', 'd': 'a', 'e': 'b', 'f': 'c', 'g': 'd', 'h': 'e', 'i': 'f', 'j': 'g', 'k': 'h', 'l': 'i', 'm': 'j', 'n': 'k', 'o': 'l', 'p': 'm', 'q': 'n', 'r': 'o', 's': 'p', 't': 'q', 'u': 'r', 'v': 's', 'w': 't', 'x': 'u', 'y': 'v', 'z': 'w'}
    '''
    return {alphabet[i]: alphabet[(i   shift) % 26] for i in range(0, 26)}

Next I need to define a function encode that takes in text and shift, and returns the text encoded. I also need to use my build_cipher function in order to do this. So far I have:

def encode(text, shift):
    '''
    Description: takes in a text string and shift. Returns the text string encoded based on the shift.
    
    >>> encode('test', -4)
    
    >>> encode('code', 5)
    
    '''
    #return (text[(i   shift) % 26] for i in range(0,26))
    #return (build_cipher(shift) for text in alphabet)
    #return (build_cipher(shift) for text in range(0,26))

Each of my attempts at the return statement are in comments at the bottom. None are working correctly and I am unsure of how to exactly do this since build_cipher returns as a dictionary. Any tips on how I could achieve this are appreciated.

CodePudding user response：

You already have created your cipher building function, now let's use it to create the cipher and apply it to each character in your text. I used here get to enable keeping a character that is not in the cipher unchanged.

def encode(text, shift):
    cipher = build_cipher(shift)
    return ''.join(cipher.get(c, c) for c in text)

Example:

>>> encode('good morning', 4)
'kssh qsvrmrk'

>>> encode('kssh qsvrmrk', -4)
'good morning'

NB. your code is currently not handling capital letters, that's something you might want to fix ;)