Hi.

This is my character frequency tool. I use it
to study text documents via the command line.

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Here's how it works:
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If you stick this script in your path and turn
on the executable flag, you should be able to
run this simply by typing 'charfreq.py'. If not,
you can always type 'python charfreq.py'. It
works all the same.

charfreq.py my_text_document.txt

This passes my_text_document.txt to charfreq.py
with the default parameters. This studies each
single character in the document. If you wish
to study pairs of characters, chance the window
to '2' with the '-w' flag.

For example, let's study the alphabet. With the
window size set to 2, here are all of the pairs:

$ echo {a..z} | tr -d ' ' > alphabet.txt
$ charfreq.py alphabet.txt -w 2
mn:    1
ab:    1
ef:    1
qr:    1
wx:    1
kl:    1
yz:    1
ij:    1
st:    1
op:    1
cd:    1
uv:    1
gh:    1

So the program will roll forward two spaces for
the next pair. This is great if you know that the
data is already divided into pairs. What if you
aren't sure. What if you want to study how many
times a letter appears after another letter (similar
to how a Hidden Markov Model works). Set the window
to 2 and the roll to 1 (I also used '-s' to skip spaces):

$ charfreq.py alphabet.txt -w 2 -r 1 -s
ab:    1
ef:    1
cd:    1
tu:    1
ij:    1
vw:    1
kl:    1
jk:    1
gh:    1
pq:    1
rs:    1
lm:    1
de:    1
bc:    1
uv:    1
yz:    1
hi:    1
no:    1
fg:    1
wx:    1
qr:    1
mn:    1
st:    1
xy:    1
op:    1

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Help Screen
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Usage: charfreq.py [options] [YOUR FILE]

Options:
  --version             show program's version number and exit
  -h, --help            show this help message and exit
  -w WINDOW, --window=WINDOW
                        Windows Size (Default WINDOW=1)
  -r ROLL, --roll=ROLL  Rolling Window (Shift window by ROLL rather than
                        WINDOW)
  -s, --skipspaces      Skip Space Characters [ \t\r\n]