python code snippets episode 1

I don’t know if a module exists that acts like the which binary. If you don’t know what which does, I’ll tell you:

• given an argument ( which represents a binary/executable found on PATH ), which tells you the first location of that binary

Here’s the code I’m using:

import os

def which(program,additional_dirs=[]):
	path = os.environ["PATH"]
	path_components = path.split(":")
	path_components.extend(additional_dirs)
	for item in path_components:
		location = os.path.join(item,program)
		if os.path.exists(location):
			return location
	return None

The code is pretty straight-forward. The function takes a string as the program name, and an optional parameter that represents additional directories to look in. The default behaviour of this functions is to search the PATH variable.