gistfile1.txt

Python 2.7.12 (default, Oct 11 2016, 05:24:00)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.38)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> mymessage = "secret message"
>>> while not len(mymessage) % 5 == 0:
...     mymessage += 'X'
...
>>> print mymessage
secret messageX
>>> mymessage_iterations = len(mymessage) / 5
>>> for i in xrange(mymessage_iterations):
...     print mymessage[i*5]
...
s
t
s
>>> for n in xrange(5):
...     for i in xrange(mymessage_iterations):
...         print mymessage[n+i*5]
...
s
t
s
e

a
c
m
g
r
e
e
e
s
X
>>> secret_message = []
>>> for n in xrange(5):
...     for i in xrange(mymessage_iterations):
...         secret_message.append(mymessage[n+i*5])
...
>>> print ''.join(secret_message)
stse acmgreeesX
>>>