Parsing environment variables in ConfigParser files

[Andrew Dalke]

Matthew Barnes:
> I'm considering submitting a patch for Python 2.4 to allow environment
> variable expansion in ConfigParser files.  [...]  I'd like to be
> able to specify something like the following in a configuration file:
>
>         [section_name]
>         data_file=${HOME}/mydata.dat

Personally, I'm against it.  The less magic the better.  Eg,
what if I have a configuration file which sets the default
configurations, so that I want the actual string
  ${HOME}/mydata.dat
in the file.  What's the escape rule for that.

Whereas as it is now I can get the string value then use
os.path.expandvars (or os.path.expanduser if I want ~home
expansion).  It's an extra couple lines of code, granted,
but it's explicit instead of implicit and less likely to introduce
subtle errors.

                    Andrew
                    dalke at dalkescientific.com