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Opinionated Batteries-Included Python 3 CLI Framework.

Project description

MILC - An Opinionated Batteries-Included Python 3 CLI Framework

MILC is a framework for writing CLI applications in Python 3. It gives you all the features users expect from a modern CLI tool out of the box:

  • CLI Argument Parsing, with or without subcommands
  • Automatic tab-completion support through argcomplete
  • Configuration file which can be overridden by CLI options
  • ANSI color support- even on Windows- with colorama
  • Logging to stderr and/or a file, with ANSI colors
  • Easy method for printing to stdout with ANSI colors
  • Labeling log output with colored emoji to easily distinguish message types
  • Thread safety

Documentation

Full documentation is on the web: https://milc.clueboard.co/

Short Example

from milc import MILC

cli = MILC('My useful CLI tool.')

@cli.argument('-c', '--comma', help='comma in output', default=True, action='store_boolean')
@cli.argument('-n', '--name', help='Name to greet', default='World')
@cli.entrypoint
def main(cli):
    comma = ',' if cli.config.general.comma else ''
    cli.log.info('Hello%s %s!', comma, cli.config.general.name)

if __name__ == '__main__':
    cli.run()

Output

$ ./hello
ℹ Hello, World!
$ ./hello --no-color
INFO Hello, World!
$ ./hello --no-comma
ℹ Hello World!
$ ./hello -h
usage: hello [-h] [-V] [-v] [--datetime-fmt GENERAL_DATETIME_FMT]
             [--log-fmt GENERAL_LOG_FMT] [--log-file-fmt GENERAL_LOG_FILE_FMT]
             [--log-file GENERAL_LOG_FILE] [--color] [--no-color]
             [--config-file GENERAL_CONFIG_FILE] [--save-config]
             [-n GENERAL_NAME] [-c] [--no-comma]

Greet a user.

optional arguments:
  -h, --help            show this help message and exit
  -V, --version         Display the version and exit
  -v, --verbose         Make the logging more verbose
  --datetime-fmt GENERAL_DATETIME_FMT
                        Format string for datetimes
  --log-fmt GENERAL_LOG_FMT
                        Format string for printed log output
  --log-file-fmt GENERAL_LOG_FILE_FMT
                        Format string for log file.
  --log-file GENERAL_LOG_FILE
                        File to write log messages to
  --color               Enable color in output
  --no-color            Disable color in output
  --config-file GENERAL_CONFIG_FILE
                        The config file to read and/or write
  --save-config         Save the running configuration to the config file
  -n GENERAL_NAME, --name GENERAL_NAME
                        Name to greet
  -c, --comma           Enable comma in output
  --no-comma            Disable comma in output

Why MILC?

Because life is too short to integrate this stuff yourself, and writing good CLIs with comprehensive functionality is harder than it needs to be.

Most of the other CLI frameworks are missing a piece of the puzzle. Maybe they have argument parsing but no config file story. Maybe they have a good story around arguments and config but don't handle logging at all. You know that you're doing the same integration work that almost everyone else is doing in their own app. Why do we duplicate so much effort?

MILC is my answer to that. It implements a common set of CLI tools that pretty much every project I have ever worked on either needed or would have benefited from. Included in MILC are answers to problems you didn't know you have:

  • Config file saving and parsing
  • Automatically overriding config options with CLI arguments
  • Automatic verbose (-v) support
  • Automatic log support
  • Built-in flags for formatting log messages and log date formats
  • Support for boolean arguments (define --foo and get --no-foo for free)
  • Battle tested and used by hundreds of users every single day

You may not use all of these features yourself, but you will have users who are very glad these options are available when they need them.

Contributing

Contributions are welcome! You don't need to open an issue first, if you've developed a new feature or fixed a bug in MILC simply open a PR and we'll review it.

Please follow this checklist before submitting a PR:

  • [ ] Format your code: yapf -i -r .
  • [ ] Generate docs: ./generate_docs
  • [ ] Add any new doc files to docs/_summary.md
  • [ ] Run tests: ./ci_tests

FAQ

Why add_argument() instead of parsing function signatures?

Because I believe in writing good CLI tools.

Before writing MILC I saw variations of the same story over and over. "I started with {Click,Docopt,Whatever} but after a while I ended up just going back to argparse." In pretty much every case as the complexity of their program grew they needed to do things argparse made easy and their framework made hard.

MILC attempts to solve this by embracing the complexity of argparse. It handles the drudgery of setting up argparse for you, but gives you an elegant means to control that complexity when you need to. When your CLI framework relies on parsing function signatures you are necessarily limited in what you can do. Function annotations make this a little better but they are not a full solution to the problem.

If you care about writing good CLI tools (and I hope you do) you will want more control over the behavior of your program than Click or Docopt give you.

Why Not Some Other CLI Framework Instead?

Whenever you release a new framework the first question you'll be asked is why you didn't just use one of the existing options instead.

As I surveyed the other tools I found that most of them only solve part of the problem, not the whole problem. Those that solve the whole problem are very hard to use or get started with, or are otherwise very heavyweight. I wanted a comprehensive framework that was easy to get started with.

Below is a list of the existing tools I have looked at and why I feel they don't fill the same need as MILC.

Name Argument Parsing Config File Logging Subcommands Subcommand Config
MILC
Argparse
ConfigParser
logging
Cement
Cliar
Click
Clize
Cogs
Defopt
Docopt
Fire
Plac

Note: This list was compiled in 2018. In 2020 I edited the list to remove dead projects but I not go searching for new projects. The time for justifying MILC's existence has passed.

Argparse

The built-in argparse module is amazing- MILC uses it under the hood. Using it directly as an end-user is complicated and error-prone however. The common patterns mean you end up putting the definition of CLI arguments in a different place from the code that uses those arguments.

Cement

https://builtoncement.com/

Cement is a very heavy MVC framework for building CLI tools. It includes all the functionality MILC provides and then some. If you're looking for an MVC framework for your tool this is the one to pick.

If you are looking for an MVC framework MILC probably isn't what you want. Use Cement instead.

Cliar

https://moigagoo.github.io/cliar/

This is an interesting library. The author makes some good points about magic and DSL's. But it requires you to write a class for your CLI. Classes are good, but not every tool should be a class.

Cliar does not support a configuration file or logging.

Click

https://github.com/pallets/click

You'd have to be a fool or incredibly sure of yourself to compete against one of Armin Ronacher's projects. :)

Click is great, and I borrowed the decorator concept from Flask before I saw Click had done the same thing. It terms of how you use it there are a lot of similarities between Click and MILC.

Where Click and MILC part ways is in the underlying implementation. MILC uses the recommended and built-in Python modules whenever possible. Under the hood MILC is just argparse, logging, ConfigParser, and other standard modules abstracted just enough to make the right thing easy. Click on the other hand uses optparser, which has been deprecated in favor of argparser, and handles a lot of functionality itself rather than dispatching to included Python modules.

MILC does not insist upon a UTF-8 environment for Python 3 the way Click does. I understand Click's stance here but I'm hoping that the ecosystem has developed enough by now to make it no longer necessary. Time will tell if my opinion changes or not.

Whether you should use Click or MILC depends on the tradeoff you want to make. Would you rather use the Python modules everyone's already familiar with or dive into a world of custom code that attempts to make everything cleaner overall? Do you want one cohesive system or do you want to pull together disparate plugins and modules to build the functionality you need?

Click does not support a configuration file or logging out of the box, but there are plugins you can get to add this and other functionality to Click.

Clize

https://github.com/epsy/clize

Clize has a nice approach with lots of mature and advanced functionality.

Clize uses function annotation to work, which may or may not fit with how you work. It also has a lot of arbitrary restrictions due to annotations, for example alt functions don't work with argument aliases.

Clize does not support a configuration file or logging.

Cogs

https://github.com/prometheusresearch/cogs

Cogs seems interesting, but has its own dedicated CLI tool named cogs. You don't create scripts directly but instead create Python functions that cogs will call. This is not a paradigm that I want to use.

Cogs does not include config file support.

defopt

https://github.com/evanunderscore/defopt

Defopt is a great tool for turning functions into CLIs. Had I found this earlier I may not have written MILC at all. But I have written MILC, and there's some things I'm still not sure about. For example, I don't see a way to have script handle both subcommand and non-subcommand operation.

Defopt does not support a configuration file or logging.

docopt

https://github.com/docopt/docopt

Docopt has a large following, and some interesting ideas. But if you are someone who does not like the idea of using comments to define behavior you will not enjoy working with docopt.

Docopt has poor error handling. You have to do your own argument validation, and even when Docopt knows the passed arguments are invalid it does not return a useful error message to the user.

Docopt does not support config files.

Fire

https://github.com/google/python-fire

Fire is an interesting idea- turn any class into a CLI. Unfortunately this is useful more as a tool for introspection than building a good CLI.

Fire does not support a configuration file or logging.

Plac

https://github.com/micheles/plac

I like his idea about scaling down, and it's part of what drove me. But I don't want to go without functionality to scale down. MILC's idea of scaling down is working well for small programs.

Plac does not support a configuration file or logging.

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