Python case insensitive file name?

Question

I need to load a file given it's name, but the name I get is case insensitive. "A.txt" could actually be "a.txt". How to do this the fast way (not generate all possible names and try each)?

Solution 1

You could list the directory the file's in (os.listdir), and see if there are matches for your filename. The matching can be done by lower-casing both filenames and comparing.

Solution 2

You can't do it without taking a directory listing and taking both the item you're looking for and each in the directory to a common case for comparison. The filesystem is case sensitive and that's all there is to it.

Here is a function (well, two) that I wrote to do it completely, matching a filename in an insensitive manner, recursively: http://portableapps.hg.sourceforge.net/hgweb/portableapps/development-toolkit/file/775197d56e86/utils.py#l78.

def path_insensitive(path):
    """
    Get a case-insensitive path for use on a case sensitive system.

    >>> path_insensitive('/Home')
    '/home'
    >>> path_insensitive('/Home/chris')
    '/home/chris'
    >>> path_insensitive('/HoME/CHris/')
    '/home/chris/'
    >>> path_insensitive('/home/CHRIS')
    '/home/chris'
    >>> path_insensitive('/Home/CHRIS/.gtk-bookmarks')
    '/home/chris/.gtk-bookmarks'
    >>> path_insensitive('/home/chris/.GTK-bookmarks')
    '/home/chris/.gtk-bookmarks'
    >>> path_insensitive('/HOME/Chris/.GTK-bookmarks')
    '/home/chris/.gtk-bookmarks'
    >>> path_insensitive("/HOME/Chris/I HOPE this doesn't exist")
    "/HOME/Chris/I HOPE this doesn't exist"
    """

    return _path_insensitive(path) or path


def _path_insensitive(path):
    """
    Recursive part of path_insensitive to do the work.
    """

    if path == '' or os.path.exists(path):
        return path

    base = os.path.basename(path)  # may be a directory or a file
    dirname = os.path.dirname(path)

    suffix = ''
    if not base:  # dir ends with a slash?
        if len(dirname) < len(path):
            suffix = path[:len(path) - len(dirname)]

        base = os.path.basename(dirname)
        dirname = os.path.dirname(dirname)

    if not os.path.exists(dirname):
        dirname = _path_insensitive(dirname)
        if not dirname:
            return

    # at this point, the directory exists but not the file

    try:  # we are expecting dirname to be a directory, but it could be a file
        files = os.listdir(dirname)
    except OSError:
        return

    baselow = base.lower()
    try:
        basefinal = next(fl for fl in files if fl.lower() == baselow)
    except StopIteration:
        return

    if basefinal:
        return os.path.join(dirname, basefinal) + suffix
    else:
        return

Solution 3

This is a simple recursive function to to the search Eli suggests above:

def find_sensitive_path(dir, insensitive_path):

    insensitive_path = insensitive_path.strip(os.path.sep)

    parts = insensitive_path.split(os.path.sep)
    next_name = parts[0]
    for name in os.listdir(dir):
        if next_name.lower() == name.lower():
            improved_path = os.path.join(dir, name)
            if len(parts) == 1:
                return improved_path
            else:
                return find_sensitive_path(improved_path, os.path.sep.join(parts[1:]))
    return None

Solution 4

Make a directory listing; and create a dictionary containing a mapping of upper-case filenames to their actual-case filenames. Then, make your input upper-case, and look for it in the dictionary.

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Comments

[Admin]

Yeah, but is it efficient? Considering the folder can have thousands of files?

[TOMKA]

@user975135: I wouldn't worry about inefficiency until you have tried this approach and it is too slow for your needs.

[Admin]

Well I have processed thousands of strings at once with Python before so I think I shouldn't ignore it if there's another way.

[Eli Bendersky]

@user975135: since this is disk reading we're talking about, I'm pretty sure that the runtime overhead of this Python code will be small, relative to the time spent by the OS querying the hard-disk and making the listing