CLI sub-command library
This is a tiny library to help you write CLI applications with many sub-commands.
pip install subc
Create your own command subclass for your application:
class MyCmd(subc.Command): pass
Then, write commands in your application which sub-class this:
class HelloWorld(MyCmd): name = 'hello-world' description = 'say hello' def run(self): print('hello world')
Finally, use your application-level subclass for creating the argument parser and running your application:
if __name__ == '__main__': MyCmd.main('description of app')
Intermediate Base Classes
You may find yourself wanting to create intermediate subclasses for your application, in order to share common functionality. For example, you might create a class for all commands which handle a single file as an argument:
class FileCmd(MyCmd): def add_args(self, parser): parser.add_args('file', help='the single file')
You can do that, so long as your intermediate subclasses are not executable. For example, given the following class hierarchy:
MyCmd* |- FileCmd* | |- AppendLineCmd | |- RemoveLineCmd |- DoSomethingElseCmd
The non-leaf commands (marked with an asterisk) will not be included as executable commands. Only leaf classes will be executable.
When the user does not provide any argument on the command-line, the default action is to raise an Exception which states “you must select a sub-command”. You can provide a default command to run instead, via the default argument to main() (or add_subcommands()). For example:
if __name__ == '__main__': MyCmd.main('description', default='help')
The above code will run the help subcommand when no subcommand is specified. Note that in this case, the default sub-command may not receive all of its expected arguments.
Shortest Prefix Aliasing
subc has an optional feature which allows the user to specify a subcommand by the shortest prefix which uniquely identifies the subcommand, or any longer prefix thereof. As an example, imagine a git command with the following sub-commands: clone, checkout, commit, cherry-pick. The shortest prefix aliasing would allow you to run “git clone” by executing git cl, since only “clone” begins with “cl”. You could also execute “git clone” with a longer prefix like git clo. The feature can be enabled by setting shortest_prefix to true in main() or add_subcommands().
This project is released under the Revised BSD license. See LICENSE.txt for details.
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