Add examples to the ConfigParser documentation.

Credits go to Thomas Lamb, who wrote this as a task in the GHOP contest.

Doc/ACKS.txt

@@ -100,6 +100,7 @@ docs@python.org), and we'll be glad to correct the problem.
 * Andrew M. Kuchling
 * Dave Kuhlman
 * Erno Kuusela
+* Thomas Lamb
 * Detlef Lannert
 * Piers Lauder
 * Glyph Lefkowitz

Doc/library/configparser.rst

@@ -359,3 +359,90 @@ The :class:`SafeConfigParser` class implements the same extended interface as
 
    .. versionadded:: 2.4
 
+
+Examples
+--------
+
+An example of writing to a configuration file::
+
+   import ConfigParser
+
+   config = ConfigParser.RawConfigParser()
+   
+   # When adding sections or items, add them in the reverse order of
+   # how you want them to be displayed in the actual file.
+   # In addition, please note that using RawConfigParser's and the raw
+   # mode of ConfigParser's respective set functions, you can assign
+   # non-string values to keys internally, but will receive an error
+   # when attempting to write to a file or when you get it in non-raw
+   # mode. SafeConfigParser does not allow such assignments to take place.
+   config.add_section('Section1')
+   config.set('Section1', 'int', '15')
+   config.set('Section1', 'bool', 'true')
+   config.set('Section1', 'float', '3.1415')
+   config.set('Section1', 'baz', 'fun')
+   config.set('Section1', 'bar', 'Python')
+   config.set('Section1', 'foo', '%(bar)s is %(baz)s!')
+   
+   # Writing our configuration file to 'example.cfg'
+   with open('example.cfg', 'wb') as configfile:
+       config.write(configfile)
+
+An example of reading the configuration file again::
+
+   import ConfigParser
+
+   config = ConfigParser.RawConfigParser()
+   config.read('example.cfg')
+
+   # getfloat() raises an exception if the value is not a float
+   # getint() and getboolean() also do this for their respective types
+   float = config.getfloat('Section1', 'float')
+   int = config.getint('Section1', 'int')
+   print float + int
+
+   # Notice that the next output does not interpolate '%(bar)s' or '%(baz)s'.
+   # This is because we are using a RawConfigParser().
+   if config.getboolean('Section1', 'bool'):
+       print config.get('Section1', 'foo')
+
+To get interpolation, you will need to use a :class:`ConfigParser` or
+:class:`SafeConfigParser`::
+
+   import ConfigParser
+
+   config = ConfigParser.ConfigParser()
+   config.read('example.cfg')
+
+   # Set the third, optional argument of get to 1 if you wish to use raw mode.
+   print config.get('Section1', 'foo', 0) # -> "Python is fun!"
+   print config.get('Section1', 'foo', 1) # -> "%(bar)s is %(baz)s!"
+
+   # The optional fourth argument is a dict with members that will take
+   # precedence in interpolation.
+   print config.get('Section1', 'foo', 0, {'bar': 'Documentation',
+                                           'baz': 'evil'})
+
+Defaults are available in all three types of ConfigParsers. They are used in 
+interpolation if an option used is not defined elsewhere. ::
+
+   import ConfigParser
+
+   # New instance with 'bar' and 'baz' defaulting to 'Life' and 'hard' each
+   config = ConfigParser.SafeConfigParser({'bar': 'Life', 'baz': 'hard'})
+   config.read('example.cfg')
+   
+   print config.get('Section1', 'foo') # -> "Python is fun!"
+   config.remove_option('Section1', 'bar')
+   config.remove_option('Section1', 'baz')
+   print config.get('Section1', 'foo') # -> "Life is hard!"
+
+The function ``opt_move`` below can be used to move options between sections::
+
+   def opt_move(config, section1, section2, option):
+       try:
+           config.set(section2, option, config.get(section1, option, 1))
+       except ConfigParser.NoSectionError:
+           # Create non-existent section
+           config.add_section(section2)
+           opt_move(config, section1, section2, option)