@main.py

Basic Examples

Instead of the verbose "boilerplate"

def main(): ...

if __name__ == '__main__':
    main()

mainpy can be used to write it as:

from mainpy import main

@main
def app(): ...

Similarly, the async boilerplate

import asyncio

async def async_app(): ...

if __name__ == '__main__':
    with asyncio.Runner() as runner:
        runner.run(async_app())

can be replaced with

from mainpy import main

@mainpy.main
async def async_app(): ...

If you cannot want to use a decorator, you can also call the decorator with the function as an argument:

def async_app(): ...

# do things before running async_app()

main(async_app)

External Libraries

Even though mainpy requires no other dependencies than typing_extensions (on Python < 3.10), it has optional support for uvloop, and plays nicely with popular CLI libraries, e.g. click and typer.

uvloop

If you have uvloop installed, mainpy will automatically call uvloop.install() before running your async main function. This can be disabled by setting use_uvloop=False, e.g.:

@main(use_uvloop=False)
async def app(): ...

Click

With click you can simply add the decorator as usual.

[!IMPORTANT] The @mainpy.main decorator must come before @click.command().

import mainpy
import click

@mainpy.main
@click.command()
def click_command():
    click.echo('Hello from click_command')

The function that is decorated with @mainpy.main is executed immediately. But a @click.group must be defined before the command function. In this case, mainpy.main should be called after all has been setup:

import mainpy
import click

@click.group()
def group(): ...

@group.command()
def command(): ...

mainpy.main(group)

Typer

A typer internally does some initialization after a command has been defined. Instead of using @mainpy.main on the command itself, you should use mainpy.main() manually:

import mainpy
import typer

app = typer.Typer()

@app.command()
def command():
    typer.echo('typer.Typer()')

mainpy.main(command)

Debug mode

Optionally, Python's development mode can be emulated by passing debug=True to mainpy.main. This does three things:

• Enable the faulthandler
• Configure warnings to display all warnings
• Runs async functions in debug mode

@main(debug=True)
def app(): ...

Installation

The mainpy package is available on pypi for Python $\ge 3.8$:

pip install mainpy

Additionally, you can install the uvloop extra which will install uvloop>=0.14 (unless you're on windows):

pip install mainpy[uvloop]