Globbing a Group of Hits

For reasons of security and the smooth-running of your program, it is a good idea to check whether an executable exists before you call it. There are two ways to do this in Python.

The glob module allows you to retrieve a listing of the current working directory and to return hits according to regular expressions. It has two methods, glob and iglob. The first returns a fixed set à la range(), while the second returns an iterator that saves on system resources. Both are called the same way:

import glob
listing = glob.glob('*.txt')

This will return a list of all text files. To check for a particular executable, simply insert the file name as the argument, and frame it in an if loop:

if glob.glob('MyExecutable.exe'): existence = 1

A second way to check for a file's existence is to use the exists() method of os.path. Recall that we used the os module previously to get our current working directory. os.path is a subset of os that is available when you import os.

import os
existence = os.path.exists('MyExecutable.exe')

The exists() method returns True if the file exists and False if it does not.