Is it possible to get a value from a dictionary entry, within that same dictionary?
I'd like to build up a list of directories whilst referencing previously added directories..

```
common_dirs = {
    'root': '/var/tmp',
    'java_path': os.path.join(dict.get('root'), 'java'),
    'application_path': os.path.join(dict.get('java_path'), 'my_app')
}

```