Feud

Not all arguments are bad.

Build powerful CLIs with simple idiomatic Python, driven by type hints.

^{About · Features · Installation · Build status · Documentation · Related projects · Contributing · Licensing}

About

Designing a good CLI can quickly spiral into chaos without the help of an intuitive CLI framework.

Feud builds on Click for argument parsing, along with Pydantic for typing, to make CLI building a breeze.

Features

Simplicity

Click is often considered the defacto command-line building utility for Python – offering far more functionality and better ease-of-use than the standard library's argparse. Despite this, for even the simplest of CLIs, code written using Click can be somewhat verbose and often requires frequently looking up documentation.

Consider the following example command for serving local files on a HTTP server.

In red is a typical Click implementation, and in green is the Feud equivalent.

Example: Command for running a HTTP web server.

# serve.py - import click + import feud + from typing import Literal - @click.command - @click.argument("port", type=int, help="Server port.") - @click.option("--watch/--no-watch", type=bool, default=True, help="Watch source code for changes.") - @click.option("--env", type=click.Choice(["dev", "prod"]), default="dev", help="Environment mode.") - def serve(port, watch, env): + def serve(port: int, *, watch: bool = True, env: Literal["dev", "prod"] = "dev"): - """Start a local HTTP server.""" + """Start a local HTTP server. + + Parameters + ---------- + port: + Server port. + watch: + Watch source code for changes. + env: + Environment mode. + """ if __name__ == "__main__": - serve() + feud.run(serve)

Click here to view the generated help screen. Help screen for the serve command. $ python serve.py --help Usage: serve.py [OPTIONS] PORT Start a local HTTP server. ╭─ Arguments ────────────────────────────────────────────────────────╮ │ * PORT INTEGER [required] │ ╰────────────────────────────────────────────────────────────────────╯ ╭─ Options ──────────────────────────────────────────────────────────╮ │ --watch/--no-watch Watch source code for changes. │ │ [default: watch] │ │ --env [dev|prod] Environment mode. [default: dev] │ │ --help Show this message and exit. │ ╰────────────────────────────────────────────────────────────────────╯

Click here to see usage examples. python serve.py 8080 python serve.py 3000 --watch --env dev python serve.py 4567 --no-watch --env prod

The core design principle behind Feud is to make it as easy as possible for even beginner Python developers to quickly create sophisticated CLIs.

The above function is written in idiomatic Python, adhering to language standards and using basic core language features such as type hints and docstrings to declare all of the relevant information about the CLI, but relying on Feud to carry out the heavy lifting of converting these language elements into a fully-fledged CLI.

Grouping commands

While a single command is often all that you need, Feud makes it straightforward to logically group together related commands into a group represented by a class with commands defined within it.

Example: Commands for creating, deleting and listing blog posts.

# post.py import feud from datetime import date class Post(feud.Group): """Manage blog posts.""" def create(id: int, *, title: str, desc: str | None = None): """Create a blog post.""" def delete(*ids: int): """Delete blog posts.""" def list(*, between: tuple[date, date] | None = None): """View all blog posts, optionally filtering by date range.""" if __name__ == "__main__": feud.run(Post)

Click here to view the generated help screen. Help screen for the post group. $ python post.py --help Usage: post.py [OPTIONS] COMMAND [ARGS]... Manage blog posts. ╭─ Options ──────────────────────────────────────────────────────────╮ │ --help Show this message and exit. │ ╰────────────────────────────────────────────────────────────────────╯ ╭─ Commands ─────────────────────────────────────────────────────────╮ │ create Create a blog post. │ │ delete Delete blog posts. │ │ list View all blog posts, optionally filtering by date range. │ ╰────────────────────────────────────────────────────────────────────╯ Help screen for the list command within the post group. $ python post.py list --help Usage: post.py list [OPTIONS] View all blog posts, optionally filtering by date range. ╭─ Options ──────────────────────────────────────────────────────────╮ │ --between <DATE DATE>... │ │ --help Show this message and exit. │ ╰────────────────────────────────────────────────────────────────────╯

Click here to see usage examples. python post.py create 1 --title "My First Post" python post.py create 2 --title "My First Detailed Post" --desc "Hi!" python post.py delete 1 2 python post.py list python post.py list --between 2020-01-30 2021-01-30

Alternatively, if you already have some functions defined that you would like to run as commands, you can simply provide them to feud.run and it will automatically generate and run a group with those commands.

# post.py

import feud
from datetime import date

def create_post(id: int, *, title: str, desc: str | None = None):
    """Create a blog post."""

def delete_posts(*ids: int):
    """Delete blog posts."""

def list_posts(*, between: tuple[date, date] | None = None):
    """View all blog posts, optionally filtering by date range."""

if __name__ == "__main__":
    feud.run([create_post, delete_posts, list_posts])

You can also use a dict to rename the generated commands:

feud.run({"create": create_post, "delete": delete_posts, "list": list_posts})

For more complex applications, you can also nest commands in sub-groups:

feud.run({"list": list_posts, "modify": [create_post, delete_posts]})

If commands are defined in another module, you can also run the module directly and Feud will pick up all runnable objects:

import post

feud.run(post)

You can even call feud.run() without providing any object, and it will automatically discover all runnable objects in the current module.

As you can see, building a CLI using Feud does not require learning many new magic methods or a domain-specific language – you can just use the simple Python you know and ❤️!

Registering command sub-groups

Groups can be registered as sub-groups under other groups. This is a common pattern in CLIs, allowing for interfaces packed with lots of functionality, but still organized in a sensible way.

Example: CLI with the following structure for running and managing a blog. blog: Group to manage and serve a blog. serve: Command to run the blog HTTP server. post: Sub-group to manage blog posts. create: Command to create a blog post. delete: Command to delete blog posts. list: Command to view all blog posts.

# blog.py import feud from datetime import date from typing import Literal class Blog(feud.Group): """Manage and serve a blog.""" def serve(port: int, *, watch: bool = True, env: Literal["dev", "prod"] = "dev"): """Start a local HTTP server.""" class Post(feud.Group): """Manage blog posts.""" def create(id: int, *, title: str, desc: str | None = None): """Create a blog post.""" def delete(*ids: int): """Delete blog posts.""" def list(*, between: tuple[date, date] | None = None): """View all blog posts, optionally filtering by date range.""" Blog.register(Post) if __name__ == "__main__": feud.run(Blog)

Click here to view the generated help screen. Help screen for the blog group. $ python blog.py --help Usage: blog.py [OPTIONS] COMMAND [ARGS]... Manage and serve a blog. ╭─ Options ──────────────────────────────────────────────────────────╮ │ --help Show this message and exit. │ ╰────────────────────────────────────────────────────────────────────╯ ╭─ Command groups ───────────────────────────────────────────────────╮ │ post Manage blog posts. │ ╰────────────────────────────────────────────────────────────────────╯ ╭─ Commands ─────────────────────────────────────────────────────────╮ │ serve Start a local HTTP server. │ ╰────────────────────────────────────────────────────────────────────╯ Help screen for the serve command in the blog group. $ python blog.py serve --help Usage: blog.py serve [OPTIONS] PORT Start a local HTTP server. ╭─ Arguments ────────────────────────────────────────────────────────╮ │ * PORT INTEGER [required] │ ╰────────────────────────────────────────────────────────────────────╯ ╭─ Options ──────────────────────────────────────────────────────────╮ │ --watch/--no-watch [default: watch] │ │ --env [dev|prod] [default: dev] │ │ --help Show this message and exit. │ ╰────────────────────────────────────────────────────────────────────╯ Help screen for the post sub-group in the blog group. $ python blog.py post --help Usage: blog.py post [OPTIONS] COMMAND [ARGS]... Manage blog posts. ╭─ Options ──────────────────────────────────────────────────────────╮ │ --help Show this message and exit. │ ╰────────────────────────────────────────────────────────────────────╯ ╭─ Commands ─────────────────────────────────────────────────────────╮ │ create Create a blog post. │ │ delete Delete blog posts. │ │ list View all blog posts, optionally filtering by date range. │ ╰────────────────────────────────────────────────────────────────────╯ Help screen for the list command within the post sub-group. $ python blog.py post list --help Usage: blog.py post list [OPTIONS] View all blog posts, optionally filtering by date range. ╭─ Options ──────────────────────────────────────────────────────────╮ │ --between <DATE DATE>... │ │ --help Show this message and exit. │ ╰────────────────────────────────────────────────────────────────────╯

Click here to see usage examples. python blog.py serve 8080 --no-watch --env prod python blog.py post create 1 --title "My First Post!" python blog.py post list --between 2020-01-30 2021-01-30

Powerful typing

Feud is powered by Pydantic – a validation library with extensive support for many data types, including:

• simple types such as integers and dates,
• complex types such as emails, IP addresses, file/directory paths, database connection strings,
• constrained types (e.g. positive/negative integers or past/future dates).

pydantic-extra-types is an optional dependency offering additional types such as country names, payment card numbers, phone numbers, colours, latitude/longitude and more.

Custom annotated types with user-defined validation functions can also be defined with Pydantic.

Example: Command for generating audio samples from text prompts using a machine learning model, and storing produced audio files in an output directory. At least one text prompt must be provided. No more than five text prompts can be provided. Each text prompt can have a maximum of 12 characters. The model is specified by a path to a file that must exist. The output directory is a path to a folder that must exist.

# generate.py import feud from pydantic import FilePath, DirectoryPath, conlist, constr def generate( prompts: conlist(constr(max_length=12), min_length=1, max_length=5), *, model: FilePath, output: DirectoryPath, ): """Generates audio from prompts using a trained model.""" if __name__ == "__main__": feud.run(generate)

Click here to view the generated help screen. Help screen for the generate command. $ python generate.py --help Usage: generate.py [OPTIONS] [PROMPTS]... Generates audio from prompts using a trained model. ╭─ Arguments ────────────────────────────────────────────────────────╮ │ PROMPTS TEXT │ ╰────────────────────────────────────────────────────────────────────╯ ╭─ Options ──────────────────────────────────────────────────────────╮ │ * --model FILE [required] │ │ * --output DIRECTORY [required] │ │ --help Show this message and exit. │ ╰────────────────────────────────────────────────────────────────────╯

Click here to see usage examples. If we run the script without prompts, we get an error that at least one prompt must be provided. $ python generate.py --model models/real_model.pt --output audio/ Usage: generate.py [OPTIONS] [PROMPTS]... Try 'generate.py --help' for help ╭─ Error ──────────────────────────────────────────────────────────────────────╮ │ 1 validation error for command 'generate' │ │ [PROMPTS]... │ │ List should have at least 1 item after validation, not 0 [input_value=()] │ ╰──────────────────────────────────────────────────────────────────────────────╯ If we provide a prompt longer than 12 characters, we also get an error. $ python generate.py "dog barking" "cat meowing" "fish blubbing" --model models/real_model.pt --output audio/ Usage: generate.py [OPTIONS] [PROMPTS]... Try 'generate.py --help' for help ╭─ Error ──────────────────────────────────────────────────────────────────────╮ │ 1 validation error for command 'generate' │ │ [PROMPTS]... [2] │ │ String should have at most 12 characters [input_value='fish blubbing'] │ ╰──────────────────────────────────────────────────────────────────────────────╯ FilePath indicates that the file must already exist, so we get an error if we provide a non-existent file. $ python generate.py "dog barking" "cat meowing" --model models/fake_model.pt Usage: generate.py [OPTIONS] [PROMPTS]... Try 'generate.py --help' for help ╭─ Error ──────────────────────────────────────────────────────────────────────╮ │ Invalid value for '--model': File 'models/fake_model.pt' does not exist. │ ╰──────────────────────────────────────────────────────────────────────────────╯ DirectoryPath indicates that the path must be a directory, so we get an error if we provide a file. $ python generate.py "dog barking" "cat meowing" --output audio.txt Usage: generate.py [OPTIONS] [PROMPTS]... Try 'generate.py --help' for help ╭─ Error ──────────────────────────────────────────────────────────────────────╮ │ Invalid value for '--output': Directory 'audio.txt' is a file. │ ╰──────────────────────────────────────────────────────────────────────────────╯

By relying on Pydantic to handle the hard work of validation, we can contain all of the required CLI constraints in a simple function signature, leaving you to focus on the important part – implementing your commands.

Highly configurable and extensible

While designed to be simpler than Click, this comes with the trade-off that Feud is also more opinionated than Click and only directly implements a subset of its functionality.

However, Feud was designed to allow for Click to seamlessly slot in whenever manual overrides are necessary.

Example: Use click.password_option to securely prompt the user for a password, but still validate based on the type hint (length should be ≥ 10 characters).

# login.py import feud from feud import click from pydantic import constr @click.password_option("--password", help="The user's password (≥ 10 characters).") def login(*, username: str, password: constr(min_length=10)): """Log in as a user. Parameters ---------- username: The user's username. """ if __name__ == "__main__": feud.run(login)

Click here to view the generated help screen. Help screen for the login command. $ python login.py --help Usage: login.py [OPTIONS] Log in as a user. ╭─ Options ──────────────────────────────────────────────────────────╮ │ * --username TEXT The user's username. [required] │ │ --password TEXT The user's password (≥ 10 characters). │ │ --help Show this message and exit. │ ╰────────────────────────────────────────────────────────────────────╯

Click here to see usage examples. $ python login.py --username alice Password: *** Repeat for confirmation: *** Usage: login.py [OPTIONS] Try 'login.py --help' for help ╭─ Error ────────────────────────────────────────────────────────────╮ │ 1 validation error for command 'login' │ │ --password │ │ String should have at least 10 characters [input_value=hidden] │ ╰────────────────────────────────────────────────────────────────────╯

Installation

You can install Feud using pip.

The latest stable version of Feud can be installed with the following command.

pip install "feud[all]"

This installs Feud with the optional dependencies:

• rich-click (can install individually with pip install "feud[rich]")
  Provides improved formatting for CLIs produced by Feud.
• pydantic-extra-types (can install individually with pip install "feud[extra-types]")
  Provides additional types that can be used as type hints for Feud commands.
• email-validator (can install individually with pip install "feud[email]")
  Provides Pydantic support for email validation.

To install Feud without any optional dependencies, simply run pip install feud.

Improved formatting with Rich

Below is a comparison of Feud with and without rich-click.

With Rich-formatted output	Without Rich-formatted output

Build status

master	dev

Documentation

• API reference: Library documentation for public modules, classes and functions.

Related projects

Feud either relies heavily on, or was inspired by the following packages. It would be greatly appreciated if you also supported the below maintainers and the work they have done that Feud has built upon.

Project	Description
Click by @pallets	Feud is essentially a wrapper around Click that takes classes and functions with type hints and intelligently 'compiles' them into a ready-to-use Click generated CLI.
Rich Click by @ewels	A shim around Click that renders help output nicely using Rich.
Pydantic by @samuelcolvin	Pydantic is a validation package that makes it easy to declaratively validate input data based on type hints. The package offers support for common standard library types, plus more complex types which can also be used as type hints in Feud commands for input validation.
Typer by @tiangolo	Typer shares a similar ideology to Feud, in that building CLIs should be simple and not require learning new functions or constantly referring to library documentation. Typer is also based on Click. Typer is a more complete library for building CLIs overall, but currently lacks support for more complex types such as those offered by Pydantic.
Thor by @rails	Though not a Python package, the highly object-oriented design of Thor (a CLI building package in Ruby) – in particular the use of classes to define command groups – greatly influenced the implementation of the feud.Group class.

Contributing

All contributions to this repository are greatly appreciated. Contribution guidelines can be found here.

We're living in an imperfect world!
^{Feud is in a public beta-test phase, likely with lots of bugs. Please leave feedback if you come across anything strange!}

Licensing

Feud is released under the MIT license.

---

Feud © 2023-2025, Edwin Onuonga - Released under the MIT license.
Authored and maintained by Edwin Onuonga.