a ConfigParser wtf moment

[grahamd at dscpl.com.au]

Sort of hard to explain, but if you put another:

list = configuration.items("core")
print list

at the end of the script, you will find that the original config hasn't
been changed.
It is a quirk of how the items() method is implemented using 'yield'
that means that
you see what you do.

In particular to use 'yield' it it necessary to create a temporary
dictionary which
contains the key/value pairs from that section of the config and then
overlay it
with the user supplied vars. Ie., the items() code has:

.        d = self._defaults.copy()
.        try:
.            d.update(self._sections[section])
.        except KeyError:
.            if section != DEFAULTSECT:
.                raise NoSectionError(section)
.        # Update with the entry specific variables
.        if vars:
.            d.update(vars)

See the last line, that will replace the value of 'xyzzy' with that
passed in
as argument to items().

To avoid this, you need to write something like:

.  list = []
.  for key in configuration.options("core"):
.     list.append((key,configuration.get("core",substitution))
.  print list

This cause me problems for a different reason, ie., that user vars keys
appear in what items() returns. I avoid using items() for this reason.