[Snippet] Case Correction in Python

[Moshe Zadka]

Hi!

Those of you who were in my lecture last Friday will remember I showed a
cute-little case correction function, which used global variables. I have
reworked that example into a class which can be adapted to different file 
mistakes you may want to allow.

Here it is for your enjoyment:

==================== cut here =================
# PathCorrect.py
# Released to the public domain by Moshe Zadka, 9.6.2000

import dircache, os, string

class PathCorrect:

        def __init__(self):
                self._cache = {}

        def correct(self, file):
                if self._cache.has_key(file):
                        return self._cache[file]
                ret = self._correct(file)
                self._cache[file] = ret
                return ret

        def _correct(self, file):
                if os.path.exists(file):
                        return file
                dir, file = os.path.split(file)
                dir = self.correct(dir)
                if not file:
                        return dir
                files = dircache.listdir(dir)
                if file in files:
                        return os.path.join(dir, file)
                file = files[map(self.hash, files).index(self.hash(file))]
                return os.path.join(dir, file)

        def hash(self, file):
                raise NotImplementedError("use subclassable")

class CaseCorrect(PathCorrect):

        def hash(self, file):
                return string.lower(file)

class UnderScoreCorrect(PathCorrect):

        def hash(self, file):
                return string.replace(file, '_', '')

def _test():
        def randomly_case(s):
                import random
                functions = [string.lower, string.upper]
                l = []
                for c in s:
                        l.append(random.choice(functions)(c))
                return string.join(l, '')
        c = CaseCorrect()
        for file in map(randomly_case,
                        map(os.path.abspath, dircache.listdir("."))):
                assert os.path.exists(c.correct(file))

if __name__=='__main__':
        _test()

====================== cut here =====================

Those of you paying attention might have noted I also presented a
reworked randomly_case function in the test function, for your silly mood
days.

# Use like:
from PathCorrect import CaseCorrect
c = CaseCorrect()
for file in sys.argv[1:]:
	try:
		print file+':', c.correct(file)
	except ValueError:
		print file, 'does not exist, casing aside'

--
Moshe Zadka <moshez at math.huji.ac.il>
http://www.oreilly.com/news/prescod_0300.html
http://www.linux.org.il -- we put the penguin in .com