Shlax: Beautiful Async Subprocess executor

Why?

In Python we now have async subprocesses which allows to execute several subprocesses at the same time. The purpose of this library is to:

• stream stderr and stdout in real time while capturing it,
• real time output must be prefixed for when you execute several commands at the time so that you know which line is for which process, like with docker-compose logs,
• output coloration in real time with regexps to make even more readable.

This code was copy/pasted between projects and finally extracted on its own.

Demo

You will find the demo script in demo.py in this repository.

Usage

Basics

Basic example, this will both stream output and capture it:

from shlax import Subprocess
proc = await Subprocess('echo hi').wait()
print(proc.rc, proc.out, proc.err, proc.out_raw, proc.err_raw)

Longer

If you want to start the command and wait for completion elsewhere then call any of start() and wait(), or both, explicitely:

proc = Subprocess('echo hi')
await proc.start()  # start the process
await proc.wait()   # wait for completion

Proc alias

Note that shlax defines an alias Proc to Subprocess so this also works:

from shlax import Proc
proc = await Proc('echo hi').wait()

Quiet

To disable real time output streaming use the quiet argument:

proc = await Subprocess('echo hi', quiet=True).wait()

Prefix

Using prefixes, you can have real time outputs of parallel commands and at the same time know which output belongs to which process:

proc0 = Subprocess('find /', prefix='first')
proc1 = Subprocess('find /', prefix='second')
await asyncio.gather(proc0.wait(), proc1.wait())

Coloration and output patching

You can add coloration or patch real time output with regexps, note that it will be applied line by line:

import sys
regexps = {
    '^(.*).py$': '{cyan}\\1',
}
await asyncio.gather(*[
    Subprocess(
        f'find {path}',
        regexps=regexps,
    ).wait()
    for path in sys.path
])

Where is the rest?

Shlax used to be the name of a much more ambitious poc-project, that you can still find in the OLD branch of this repository. It has been extracted in two projects with clear boundaries, namely sysplan and podplan which are still in alpha state, although Shlax as it now, is feature complete and stable.