YARU (やる)

Write and manage your project's development scripts with modern Python syntax.

The project's name comes from the Japanese verb やる, which means "to do".

Highlights

• 🗂️ Lightweight package with zero dependencies.
• 🐍 Supports modern Python versions (>=3.12).
• 🚀 Simply write your development scripts as Python functions.
• 🖥️ Supports macOS, Linux, and Windows.

Installation

If using the uv package manager:

uv add --dev yaru

If using pip:

pip install yaru

Documentation

Yaru's documentation is available at https://github.com/c0dearm/yaru.

Features

A single decorator to rule them all

Simply decorate your Python functions to convert them into cli commands:

# :commands.py file

from typing import Annotated
from yaru import Arg, Context, command


# Add two numbers
@command
def add_numbers(c: Context, a: int, b: int) -> None:
    """Given `a` and `b`, print the sum of both numbers to stdout."""

    print(a + b)

The decorated functions must be discovered by yaru, so they need to be in a module named commands at the root of your project, for example a commands.py file.

The add_numbers command is now invokable through the cli, this is the output of yaru --help:

usage: yaru [-h] {add-numbers} ...

Project's development commands

positional arguments:
  {add-numbers}
    add-numbers  Add two numbers

options:
  -h, --help     show this help message and exit

For specific help on the command usage, you can do: yaru add-numbers --help:

usage: yaru add-numbers [-h] a b

Given `a` and `b`, print the sum of both numbers to stdout.

positional arguments:
  a
  b

options:
  -h, --help  show this help message and exit

Running the command yaru add-numbers 42 69 in your terminal will output 111.

Automated command metadata

The help text for the cli command is automatically parsed from the comments immiediatelly preceding the decorated function. Similarly, the command's description is obtained from the function's docstrings.

Moreover, you can use annotated type hints on your function's arguments in order to add help texts to the command's parameters too:

# :commands.py file

from typing import Annotated
from yaru import Arg, Context, command


# Add two numbers
@command
def add_numbers(
    c: Context,
    a: Annotated[int, Arg(help="First operand")],
    b: Annotated[int, Arg(help="Second operand")],
) -> None:
    """Given `a` and `b`, print the sum of both numbers to stdout."""

    print(a + b)

The add-numbers cli help will now display as:

usage: yaru add-numbers [-h] a b

Given `a` and `b`, print the sum of both numbers to stdout.

positional arguments:
  a           First operand
  b           Second operand

options:
  -h, --help  show this help message and exit

Optional arguments

If you define the function's arguments as optional (keyword arguments with defaults), yaru will treat them as such in the cli. For example:

# :commands.py file

from yaru import Context, command


@command
def say_something(c: Context, phrase: str, twice: bool = False) -> None:
    print(phrase)
    if twice:
        print(phrase)

Will be handled like this:

usage: yaru say-something [-h] [--twice | --no-twice] phrase

positional arguments:
  phrase

options:
  -h, --help           show this help message and exit
  --twice, --no-twice

Context to run commands in a shell

You may have noticed an extra first Context argument in all the commands. This is automatically injected by yaru and provides a handy method run to execute instructions in your shell.

Going back to the example of number addition, we could do this in bash instead of python:

# :commands.py file

from yaru import Context, command


# Add two numbers
@command
def add_numbers(c: Context, a: int, b: int) -> None:
    c.run(f"echo $(({a} + {b}))")

The behavior when executed is exactly the same.

Contributing

We welcome contributions! Please read our CONTRIBUTING.md file for guidelines on how to contribute to this project.

Acknowledgements

Yaru exists thanks to pyinvoke, which was the main inspirer.

License

Yaru is licensed under the MIT license (LICENSE or https://opensource.org/licenses/MIT)