Introduction to Python (by Ilan Schnell)

The exec statement

Executes a string of a python code.

Suppose you which to write a program which reads a config-file ~/.myprogrc:

# Configuration file for my progamm
verbose  = True
errorlog = "/var/log/myprogram/error.log"
colors   = { "fore" : "#ae2020",
             "back" : "#f7d8c2" }

Instead of scanning, parsing and analyzing the config-file yourself, write the config-file in python syntax and let python do all the work for you:

#!/usr/bin/python
import os.path
exec(file(os.path.expanduser('~/.myprogrc')))
if verbose:
    print 'Welcome to my program!'
    print 'Background-color is:', colors['back']

Running the program in a shell:

$ ./myprog.py
Welcome to my program!
Background-color is: #f7d8c2