Merging back into solutions

[cipher-training.git] / cipher.py

diff --git a/cipher.py b/cipher.py
index bde9ea1edae60438c4ea131690c9221c689f1eab..d2438b720693c6abc231b827fe26a8d5ce52dddf 100644 (file)
--- a/cipher.py
+++ b/cipher.py
@@ -16,6 +16,52 @@ for a in range(26):
         modular_division_table[b][c] = a
 
 
+def every_nth(text, n, fillvalue=''):
+    """Returns n strings, each of which consists of every nth character,
+    starting with the 0th, 1st, 2nd, ... (n-1)th character
+
+    >>> every_nth(string.ascii_lowercase, 5)
+    ['afkpuz', 'bglqv', 'chmrw', 'dinsx', 'ejoty']
+    >>> every_nth(string.ascii_lowercase, 1)
+    ['abcdefghijklmnopqrstuvwxyz']
+    >>> every_nth(string.ascii_lowercase, 26) # doctest: +NORMALIZE_WHITESPACE
+    ['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']
+    >>> every_nth(string.ascii_lowercase, 5, fillvalue='!')
+    ['afkpuz', 'bglqv!', 'chmrw!', 'dinsx!', 'ejoty!']
+    """
+    split_text = chunks(text, n, fillvalue)
+    return [''.join(l) for l in zip_longest(*split_text, fillvalue=fillvalue)]
+
+def combine_every_nth(split_text):
+    """Reforms a text split into every_nth strings
+
+    >>> combine_every_nth(every_nth(string.ascii_lowercase, 5))
+    'abcdefghijklmnopqrstuvwxyz'
+    >>> combine_every_nth(every_nth(string.ascii_lowercase, 1))
+    'abcdefghijklmnopqrstuvwxyz'
+    >>> combine_every_nth(every_nth(string.ascii_lowercase, 26))
+    'abcdefghijklmnopqrstuvwxyz'
+    """
+    return ''.join([''.join(l)
+                    for l in zip_longest(*split_text, fillvalue='')])
+
+def chunks(text, n, fillvalue=None):
+    """Split a text into chunks of n characters
+
+    >>> chunks('abcdefghi', 3)
+    ['abc', 'def', 'ghi']
+    >>> chunks('abcdefghi', 4)
+    ['abcd', 'efgh', 'i']
+    >>> chunks('abcdefghi', 4, fillvalue='!')
+    ['abcd', 'efgh', 'i!!!']
+    """
+    if fillvalue:
+        padding = fillvalue[0] * (n - len(text) % n)
+    else:
+        padding = ''
+    return [(text+padding)[i:i+n] for i in range(0, len(text), n)]
+
 def deduplicate(text):
     """If a string contains duplicate letters, remove all but the first. Retain
     the order of the letters.