which.py is a small GNU-which replacement. It has the following features:

• it is portable (Windows, Linux, Mac OS X, Un*x);
• it understands PATHEXT and "App Paths" registration on Windows (i.e. it will find everything that start does from the command shell);
• it can print all matches on the PATH;
• it can note "near misses" on the PATH (e.g. files that match but may not, say, have execute permissions); and
• it can be used as a Python module.

Getting Started

Currently the best intro to using which.py as a module is its module documentation. Either install which.py and run:

pydoc which

take a look at which.py in your editor or TODO here, or read on. Most commonly you'll use the which() method to find an executable:

>>> import which
>>> which.which("perl")
'/usr/local/bin/perl'

Or you might want to know if you have multiple versions on your path:

>>> which.whichall("perl")
['/usr/local/bin/perl', '/usr/bin/perl']

Use verbose to see where your executable is being found. (On Windows this might not always be so obvious as your PATH environment variable. There is an "App Paths" area of the registry where the start command will find "registered" executables -- which.py mimics this.)

>>> which.whichall("perl", verbose=True)
[('/usr/local/bin/perl', 'from PATH element 10'),
 ('/usr/bin/perl', 'from PATH element 15')]

You can restrict the searched path:

>>> which.whichall("perl", path=["/usr/bin"])
['/usr/bin/perl']

There is a generator interface:

>>> for perl in which.whichgen("perl"):
...     print "found a perl here:", perl
... 
found a perl here: /usr/local/bin/perl
found a perl here: /usr/bin/perl

An exception is raised if your executable is not found:

>>> which.which("fuzzywuzzy")
Traceback (most recent call last):
  ...
which.WhichError: Could not find 'fuzzywuzzy' on the path.
>>>

There are some other options too:

>>> help(which.which)
...

Run which --help to see command-line usage:

$ which --help
Show the full path of commands.

Usage:
    which [<options>...] [<command-name>...]

Options:
    -h, --help      Print this help and exit.
    -V, --version   Print the version info and exit.

    -a, --all       Print *all* matching paths.
    -v, --verbose   Print out how matches were located and
                    show near misses on stderr.
    -q, --quiet     Just print out matches. I.e., do not print out
                    near misses.

    -p <altpath>, --path=<altpath>
                    An alternative path (list of directories) may
                    be specified for searching.
    -e <exts>, --exts=<exts>
                    Specify a list of extensions to consider instead
                    of the usual list (';'-separate list, Windows
                    only).

Show the full path to the program that would be run for each given
command name, if any. Which, like GNU's which, returns the number of
failed arguments, or -1 when no <command-name> was given.

Near misses include duplicates, non-regular files and (on Un*x)
files without executable access.