implemented the creation of random one-time pads of specified length, defaulting to width of 72

onetimepad.py

@@ -1,3 +1,4 @@
+import random
 
 
 def encode(msg, pad):
@@ -6,3 +7,53 @@ def encode(msg, pad):
 
 def decode(msg, pad):
     return msg
+
+
+def create_pad(length, width=72):
+    chars = _create_chars_for_pad(length)
+    lines = _chunk_chars_into_lines(chars, width=width)
+    return lines
+
+
+def _create_chars_for_pad(length):
+    chars = []
+    for char in range(length):
+        chars.append(_AS_ALPHA[random.randint(1, 25)])
+    return ''.join(chars)
+
+
+def _chunk_chars_into_lines(chars, width=72):
+    lines = []
+    for chunk in _as_line_chunks(chars, width=width):
+        lines.append(chunk)
+    return '\n\n\n'.join(lines)
+
+
+def _as_line_chunks(chars, width=72):
+    chunk = []
+    for char in chars:
+        chunk.append(char)
+        if len(chunk) == width:
+            yield ''.join(chunk)
+            chunk = []
+    if len(chunk) < width:
+        chunk += (['.'] * (width - len(chunk)))
+    yield ''.join(chunk)
+
+
+def _mk_as_alpha():
+    as_alpha = dict()
+    a_chr = ord('A')
+    past_j = False
+
+    for char in range(26):
+        letter = chr(a_chr + char)
+        if letter != 'J':
+            key = char + (1 if not past_j else 0)
+            as_alpha[key] = letter
+        else:
+            past_j = True
+    return as_alpha
+
+
+_AS_ALPHA = _mk_as_alpha()

test_onetimepad.py

@@ -5,17 +5,14 @@ import onetimepad as OT
 
 
 class TestOneTimePad(unittest.TestCase):
-    pad = 'THISISMYONETIMEPADANDITISNOTESPECIALLYBIG' \
-          'BUTITISBIGENOUGHFORMYUSESIFYOUDONTMINDTHX'
 
-    def test_encode(self):
+    def test_mk_as_alpha_excludes_j(self):
-        enc = OT.encode(IN_MSG, self.pad)
+        self.assertTrue('J' not in OT._AS_ALPHA.values())
-        self.assertEqual(EXPECTED_ENCODED, enc)
 
-    def test_decode(self):
+    def test_mk_as_alpha_dict_has_25_members(self):
-        dec = OT.decode(EXPECTED_ENCODED, self.pad)
+        self.assertEqual(25, len(OT._AS_ALPHA.items()))
-        self.assertEqual(IN_MSG, dec)
 
-
+    def test_creates_pad_of_desired_length(self):
-IN_MSG = 'TWOBYFOURBOARDSONEHUNDREDCOUNTLENGTHEIGHTFEET'
+        for width in (72, 33, 99, 111):
-EXPECTED_ENCODED = 'huteshusoahutseohusoaeutoaehusoat'
+            pad = OT.create_pad(2000, width=width)
+            self.assertEqual(2000, len((''.join(pad.split())).strip('.')))