How to exclude DEFAULTs from Python ConfigParser .items()?

Question

I'm using ConfigParser to load in data from a configuration file as follows: test.conf: ``` [myfiles] fileone: %(datadir)s/somefile.foo filetwo: %(datadir)s/nudderfile.foo ``` load.py: ``` import ConfigParser config = ConfigParser.ConfigParser({'datadir': '/tmp'}) config.read('test.conf') print config.items('myfiles') print config.get('myfiles', 'datadir') ``` Output: ``` $ python load.py [('datadir', '/tmp'), ('filetwo', '/tmp/nudderfile.foo'), ('fileone', '/tmp/somefile.foo')] /tmp ``` I'm surprised that the defaults for variable substitution `('datadir', '/tmp')` are showing up as part of the .`items()` and `.get()` returns, as if they were values in the configuration file. Is this behavior expected? Any work arounds, so that I can simply iterate `.items()` without getting the default dictionary values in there, but still using the magic interpolation? Reference: http://docs.python.org/library/configparser.html Thanks! Update: It's been pointed out that this is the expected behavio…

Accepted Answer

Generally, I've found the configparser.Configparser class very helpful, but also lacking. Others have, too.

However, it can be subclassed and extended, sometimes nicely, sometimes not so nicely (=very implementation dependent)

Here's a solution for your problem, tested in Python3:

```
class ConfigParser(configparser.ConfigParser):
    """Can get options() without defaults
    """
    def options(self, section, no_defaults=False, **kwargs):
        if no_defaults:
            try:
                return list(self._sections[section].keys())
            except KeyError:
                raise NoSectionError(section)
        else:
            return super().options(section, **kwargs)
```

This is one of the bad examples, because it is partially copying the source code of `options()`. It would be nicer if the configparser base class `RawConfigParser` would provide an internal getter of options `_options(self, section)` which would incorporate the exception cast, and a `options()` which would make use of that. Then, in subclassing we could reuse the `_options()`.

For Python 2, I believe the only change is the `super()` call to `super(ConfigParser,self)`.

You can then use:

```
print config.options('myfiles', no_defaults=True)
```

And also use that list to iterate.

How to exclude DEFAULTs from Python ConfigParser .items()?

Solution

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