I'm proposing a small modification to Configman to add named arguments to its Swiss Army Knife feature set. Neglected in the first versions of Configman, I think this proposal will be very useful. So what I'm I talking about?
It's the arg1, arg2, arg3 that I'm interested in here. Normally, you'd access these with sys.args without configman or config.args with configman. They come to the programmer as an uninterpreted list of strings. I'm proposing treating them just like switches. We should be able to define what is expected: the position, defaults, conversion functions, actions to take, just like the command line switches. The end result to the programmer should be something that looks like this:
In other words, from the programmers perspective, they're just values passed into the program with the same access method and priority as command line switches. In fact, with a minor change to the configman Option object, they can be used to specify both switches and arguments:
Within the program, this could be accessed as:
From the users perspective, the command line can be used like this:
Notice that the actions can be specified as either positional arguments or as switches. If you do one then the other is automatically disallowed to prevent conflicts. By treating positional arguments in the same manner as switches, we get the benefit of configman's dependency injection. Say the first positional argument is the action and that corresponds with the name of a function. Because we specified the converter for the action argument to load a matching Python object from the scope, config.action will be a callable function:
Which will yield this user experience:
Notice that because the action has no default, action is required, there are no brackets around it in help. However, if you specify it as a switch, the necessity to use it as an argument goes away.
I think this is pretty cool because it makes subcommands and subcommand help simple. The list of options and additional arguments are loaded dynamically from the classes (or functions) that the user specifies on the command line.