Introduction

When trying to create Python applications that provide a convenient and easy to use and write command line interface (CLI), there is no real option. One can either create a simple conditional chain and read using the input function, but lose most of the strengths of a “rich” CLI such as a unix shell like Bash or Zsh. Or you can try and implement an application using the include cmd_ module which provides a well set up readline interface, but adding in commands, help text for those commands, and enabling tab completion is confusing and unintuitive.

The goal of WingCommander is to provide a “pythonic” interface for writing reusable functions that can be added into a common CLI application class that can be easily executed and interacted with from the commandline. The main goals are:

• pythonic: meaning the interface for adding and configuring commands for the application should use common python concepts and leverage built in features of the language
• extensible: adding commands to an application, replacing built in functionality, or adding in additional functionality should all be intuitive and easily achieved.
• intuitive: it should not be frustrating to switch from using a common unix shell like Zsh or Bash into a WingCommander based application, meaning things like tab completion and other common helper commands all carry through

How is this Pythonic?

The interface makes heavy use of decorators to add additional functionality and definition to a simple python function. The decorators are meant to do the heavy lifting and interfacing with the internal interface for the CLI application. This includes generating completions for a command based on any state of the command line, using the docstring of the function to provide the helper text for the command, and adding “smart” parsing rules for flags passed into a command (having -d and --debug mean the same thing).

If there is any point where how to implement some included functionality is confusing or jarring, file and issue and it should be addressed. This module is meant to make writing CLI applications easy, not confusing.

Extending

All of the included functionality uses simple interfaces that are also exposed by the module. So anything that is currently being done should also be possible to quickly reimplement with your own changes. None of those nested private attributes and methods that you can’t easily call or override.

Intuitive

Being a big shell user, it is paramount for a CLI application to work in the same sorts of ways as other commands in a shell. Things such as piping, redirecting input and output, tab completion, history searching, among others are all either implemented, being implemented, or on the roadmap. If there is some common shell feature that is missing, file a feature request for it if it is not already on the Ideas page.