Text Translator

#!/usr/bin/python

# One thing you might notice about this code is that, despite being a
# cheap one-shot program, it still accommodates more than just "LOLSpeak".
# You could even implement ROT13 by simply defining it in the
# 'translations' file.

# Surprised as I am to say it, this challenge is actually an excellent
# example of separating your code from your data. The suggestion to put the
# translation table in a separate file prevents you from making a big, ugly,
# inflexible clusterfuck of code.

# So props to the guys behind that 11-hour-long video. You actually did address
# quite a lot of issues that most beginner tutorials tend to neglect.

import sys

class NoTransError: pass
class NoFileError: pass

def seek_back(string, pos, char):
    s = pos
    e = pos
    while string[s] != char and s >= 0:
        s -= 1
    return string[s+1:e]

def get_text(fname):
    try:
        f = open(fname, 'r')
        buf = f.read()
        f.close()
    except IOError:
        print "Couldn't read file '%s'." % fname
        return 0

    return buf

def get_translations(fname):
    # Using CSV would be simple and all, but I prefer a challenge, so I made up my own format.
    # Also, coding isn't about laziness; it's about not repeating yourself. Worry about data duplication and readability; not how many keystrokes/lines you can save.
    sbuf = get_text(fname)
    if sbuf == 0:
        return 0
    keys = []
    vals = []
    i = 1
    while 1:
        if i >= len(sbuf): break
        if sbuf[i] == ':':
            keys.append(seek_back(sbuf, i, '\n'))
        elif sbuf[i] == '\n':
            vals.append(seek_back(sbuf, i, ':'))
        i += 1
    return zip(keys,vals)

def objectify(arr):
    # This is literally just to make it easier to read. trans[i]['key'] is more obvious than trans[i][0].
    if arr == 0:
        return 0
    buf = []
    for el in arr:
        buf.append({
            "key":   el[0],
            "value": el[1]
        })
        # Interesting thing to point out here.
        # Python calls these ~dictionaries~
        # JavaScript calls them ~objects~
        # PHP calls them ~associative arrays~
        # C++ calls them ~structs~
    return buf

def print_usage():
    print "Usage: %s [options]" % sys.argv[0]
    print "Options:"
    print "    -f [file]  specify file to use for message string.    Default: msg"
    print "    -t [file]  specify file to use for translation table. Default: translations"
    print "    -m [text]  pass the message string as an argument"
    print "    -h         show this help"
    print "Example: %s -m \"LOL WTF was that!?\" -t translations" % sys.argv[0]

def main():
    if len(sys.argv) > 1:
        i = 0
        msg = 0
        while 1:
            if i >= len(sys.argv):
                break
            if sys.argv[i] == '-f':
                msg = get_text(sys.argv[i+1])
                if msg == 0:
                    raise NoFileError
                i += 1
            elif sys.argv[i] == '-t':
                trans = objectify(get_translations(sys.argv[i+1]))
                if trans == 0:
                    raise NoTransError
                i += 1
            elif sys.argv[i] == '-m':
                msg = sys.argv[i+1]
                i += 1
            elif sys.argv[i] == '-h':
                print_usage()
                return 0
            i += 1
    else:
        print_usage()
        return 1

    for pair in trans:
        msg = msg.replace(pair['key'], pair['value'])
    print msg

try:
    ret = main()
    if ret:
        print "Shell returned an error code '%u'" % ret
except NoTransError:
    print "Please define a 'translations' file (or use -t) to remedy this."
    print "The format is 'Symbol:Translation'"
    print "For example, \"LOL:laughing out loud\""
except NoFileError:
    print "Bad File."
except:
    print "Unknown Error."