named group clear solution for Vigenere Cipher by gyahun_dash - python coding challenges

Enable Javascript in your browser and then refresh this page, for a much enhanced experience.

named group solution in Clear category for Vigenere Cipher by gyahun_dash

import itertools as it, operator as op, re, string

def subchr(text1, text2, alphabet=string.ascii_uppercase):
    seq1, seq2 = [map(alphabet.index, t) for t in (text1, text2)]
    return ''.join(alphabet[i] for i in map(op.sub, seq1, it.cycle(seq2)))

def decode_vigenere(old_decrypted, old_encrypted, new_encrypted):
    keyword = subchr(old_encrypted, old_decrypted)
    match = re.match(r'(?P.+)(?P=repeat)|(?P.+)', keyword)
    return subchr(new_encrypted, match.group('repeat') or match.group('whole'))

Nov. 6, 2014

Comments:

Winandfx on Feb. 2, 2015, 7:18 p.m.
Under Win7: <blockquote> unknown specifier: ?P. </blockquote> It's ok? And what's a group 'whole'? I don't see its definition

gyahun_dash on May 5, 2015, 7:20 p.m.
I wrote the regexp as follows, but keywords in the brackets are moved for unexplained reasons. <pre class='brush: python'>match = re.match(r'(?P<repeat>.+)(?P=repeat)|(?P<whole>.+)', keyword) </pre>

fed.kz on Sept. 27, 2018, 9 a.m.
Could you explain what mean your pattern in line 9?

gethappy on Feb. 28, 2015, 9:39 p.m.
It's not clear for me. Could you explain function "subchr"?

gyahun_dash on May 5, 2015, 8:03 p.m.
Purpose of subchr is to get keyword by subtracting decrypted text from encrypted text, and decrypted text by subtracting keyword from encrypted text. For subtraction, I convert texts to lists of integers[0 - 25]: <pre class='brush: python'>seq1, seq2 = [map(alphabet.index, t) for t in (text1, text2)] # text1, text2 = 'OIWWC', 'HELLO' # -> seq1, seq2 = [15, 9, 23, 23, 3], [8, 5, 12, 12, 15] </pre> Then, I get new list of integers[-25 - 25] by subtracting: <pre class='brush: python'>map(op.sub, seq1, seq2) # -> [7, 4, 11, 11, -12] </pre> Finally, I get the candidate of keyword or decrypted text by converting the list to text: <pre class='brush: python'>''.join(alphabet[i] for i in map(op.sub, seq1, seq2)) # -> 'HELLO' </pre> itertools.cycle is used when new text is longer than old text: <pre class='brush: python'>''.join(alphabet[i] for i in map(op.sub, seq1, it.cycle(seq2))) # new_encrypt = 'SUPERCALIFRAGILISTICEXPIALIDOCIOUS' # cycle(key) = 'HELLOHELLOHELLOHELLOHELLOHELLOHELL' </pre>

vananabu on Sept. 11, 2015, 3:19 p.m.
Good work with "re"

ljy95135 on May 31, 2016, 6:12 a.m.
It's great, I use more than 50 lines to solve it. Thx for sharing!

U.V on Feb. 16, 2023, 1:42 p.m.
I have checked solution and get assertion error at test <pre class='brush: python'> assert decode_vigenere(u"AAAAAAAAA", u"ABABABABC", u"ABABABABC") == "AAAAAAAAA", "ABABABABC" </pre> where valid key is "ABABABABC", but not "ABAB"

Blizzard

0 %

You ClassRoom Demo is Ready With the new tool CheckiO ClassRoom, you will be able to analyze your students' progress, have your own leaderboard, change missions order on the map, and so on.