Coded Correspondence Help

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1

Hello, I’m struggling with the Vignère cypher part of this project. The first part successfully produces a keyword_string that has the message with the keyword, but the second part does not produce any comprehensible message and I cannot figure out what issue is. This is my code so far (the provided solution, commented out on the bottom, doesn’t work in the second part either):

def vig_decoderalphabet = "abcdefghijklmnopqrstuvwxyz" punctuation = " ,!?'." message = "dfc aruw fsti gr vjtwhr wznj? vmph otis! cbx swv jipreneo uhllj kpi rahjib eg fjdkwkedhmp!" key = "friends"(string, keyword): keyword_string = " " keyword_index = 0 for letter in string: if letter not in punctuation: keyword_string += keyword[(keyword_index) % len(keyword)] keyword_index += 1 else: keyword_string += letter decoded_message = " " keyword_index = 0 for letter in string: if letter not in punctuation: decoded_message += alphabet[(alphabet.find(letter) - alphabet.find(keyword_string[keyword_index])) % 26] keyword_index += 1 else: decoded_message += letter #for i in range(0, len(string)): #if not string[i] in punctuation: #ln = alphabet.find(string[i]) - alphabet.find(keyword_string[i]) #decoded_message += alphabet[ln % 26] # else: # decoded_message += string[i] return decoded_message print(vig_decoder(message, key))

Any help would be greatly appreciated!

2

The codebyte had the def in the wrong place, so I moved it just before the line that has keyword_string
and I fixed the indentations appropriately.

You added spaces and other stuff to keyword_string, so you should increment keyword_index in the second loop even if the current letter is a space or other punctuation (put the keyword_index += 1 outside the if-statement in the loop, but still in the loop)
Also, you did not start keyword_string as an empty string, you initailized it to be a string that has a space in it,
so keyword_index should start at 1, not 0 for the second loop.

alphabet = "abcdefghijklmnopqrstuvwxyz"
punctuation = " ,!?'."
message = "dfc aruw fsti gr vjtwhr wznj? vmph otis! cbx swv jipreneo uhllj kpi rahjib eg fjdkwkedhmp!"
key = "friends"

def vig_decoder(string, keyword):
    keyword_string = " "
    keyword_index = 0  # used to iterate through keyword
    for letter in string:
        if letter not in punctuation:   
            keyword_string += keyword[(keyword_index) % len(keyword)]
            keyword_index += 1  # increment  
        else:
            keyword_string += letter
    decoded_message = " "
    keyword_index = 1  # used to iterate through keyword_string
    for letter in string:
        if letter not in punctuation:
            decoded_message += alphabet[(alphabet.find(letter) - alphabet.find(keyword_string[keyword_index])) % 26]
        else:
            decoded_message += letter
        keyword_index += 1  # increment outside of if - else stuff
    """  
    #for i in range(0, len(string)):
        #if not string[i] in punctuation:
            #ln = alphabet.find(string[i]) - alphabet.find(keyword_string[i])
           #decoded_message += alphabet[ln % 26]
       # else:
           # decoded_message += string[i]
    """
    return decoded_message

print(vig_decoder(message, key))