See also:

[ 1399309 ] ConfigParser to save with order
[ 1371075 ] ConfigParser to accept a custom dict to
allow ordering

The attached patch adds a new method, update_file, to
RawConfigParser.  This method is similar to the
existing write method, but preserves blank lines,
comments, and ordering, as requested many times on
python-dev and python-list.  These are the three
requirements that Guido specified in January 2005.

IMO the attached patch is better than 1399309 because
it includes all the functionality (passing a pointer to
an empty file results in a sorted write() output), but
is completely backwards compatible as write() is
unchanged.    The addition of preserving comments is
also essential for many applications.

IMO the attached patch is better than 1371075 because
the latter really requires a custom class (e.g. the
third party one suggested) in order to be useful.  It
also doesn't address the issue of preserving comments.

The attached patch is essentially a tidied up version
of the one included with SpamBayes (in the
OptionClass.py module), which is used extensively
within SpamBayes (and has been for several years).

Also attached are additional unittests for the new
method, and a documentation patch.

Please let me know if there are recommended changes.

This patch does not address any of the additional
ConfigParser improvements that have been suggested at
various times.