My solution for http://puzzles.bostonpython.com/poetry.html

bostonpythonsol1.py

data = '''a narrow fellow in the grass
occasionally rides;
you may have met him, did you not,
his notice sudden is.

the grass divides as with a comb,
a spotted shaft is seen;
and then it closes at your feet
and opens further on.

he likes a boggy acre,
a floor too cool for corn.
yet when a child, and barefoot,
i more than once, at morn,

have passed, i thought, a whip-lash
unbraiding in the sun,
when, stooping to secure it,
it wrinkled, and was gone.

several of nature's people
i know, and they know me;
i feel for them a transport
of cordiality;

but never met this fellow,
attended or alone,
without a tighter breathing,
and zero at the bone.'''

import re

def getchars(data):
    return re.findall("([a-zA-Z]{1})", data)
    return 

def print_mapping():
    chars = getchars(data)
    mapping = dict(zip(map(chars.count,chars), chars))
    print "\n".join("%s=>> %s"%(x,y) for x,y in sorted(mapping.items()))

print_mapping()

def encode(word):
    chars = getchars(data)
    reverselookup = dict(zip(chars, map(chars.count,chars)))
    return map(reverselookup.get, word)

def decode(cypher):
    chars = getchars(data)
    lookup = dict(zip(map(chars.count,chars), chars))
    return "".join(map(lookup.get, cypher))

assert(encode("enter") == [ 56,38, 44, 56,29])
assert(encode("zebra") == [1,56,7,29,42] )

cypher = [56,38,44,56,29]
print "Answer is '%s'"%decode(cypher)