pylivedev 1.2.2

Python Live Development tool.

Description

I created PyLiveDev because I work a lot in the microservices/REST space and found constantly having to run/restart services while developing and keeping track of multiple logs in separate windows, to be, quite frankly, a pain in my ass.

Inspired by live updates while using create-react-app in development, I wanted to see if there was a way I could make a python program run multiple services and keep track of the files imported. This way if anything changed it could automatically restart those services and save time while developing. As a bonus, piping all stdout/stderr to one screen so I could immediately see if I wrote bad code or was returning something unexpected.

It works by you creating a JSON configuration file called .pylivedev in the root of your python project and adding an Object member for each unique process, then running pylivedev from the root of your project.

Install

foo@bar:~$ pip install pylivedev

Warning

If you are using PyLiveDev on a Linux kernel 2.6+, you may at some point run into an issue where you see red errors like the following:

File "some/path.py" could not be tracked: (24, 'inotify instance limit reached')

File "some/path.py" could not be tracked: (28, 'inotify watch limit reached')

This is due to limits in an underlying library. When this happens adjust the following settings in your /etc/sysctl.conf file (will require root access):

fs.inotify.max_user_instances=256
fs.inotify.max_user_watches=16384

The defaults are 128 and 8192, so adjust accordingly then reboot. Increase as necessary until PyLiveDev stops reporting issues tracking files.

Note, that if you use vscode, it will try to track every single file in a project, be aware of how many files/folders in your projects, and make sure you hide things like node_modules if you're using node in your projects. Many node based auto-build development systems, create-react-app, vite, nextjs, and others will also watch files, so it's a common problem for developers.

Run

foo@bar:~$ pylivedev

Configuration

{
	"rest": {
		"command": "rest",
		"mode": "module",
		"tracked": false,
		"python": "/venv/my_project/bin/python",
		"arguments": ["-v"],
		"additional_files": ["config.json"],
		"unbuffered": true,
		"verbose": false
	}
}

Defaults

You can also use the special __default__ member to store values that will be the same across processes. Anything in the proccess config will always overwrite the defaults.

{
	"__default__": {
		"python": "/venv/my_project/bin/python",
		"mode": "module",
		"additional_files": ["config.json"],
	},

	"main": {
		"command": "nodes.rest.main"
	},

	"admin": {
		"command": "nodes.rest.admin"
	},

	"external": {
		"command": "nodes.external"
	},

	"websocket": {
		"command": "daemons.websocket"
	}
}

The above would work for a file structure like the following

my_project/
|-- daemons/
	|-- __init__.py
	|-- websocket.py
|-- nodes/
	|-- rest/
		|-- __init__.py
		|-- admin.py
		|-- main.py
	|-- __init__.py
	|-- external.py
|-- records/
	|-- __init__.py
|-- .pylivedev
|-- config.json

If, for example, nodes/rest/main.py imported the following:

from time import time
from . import Rest
from records import User

class Main(Rest):
	pass

PyLiveDev would end up with the following list of files to watch/observe for changes

• config.json
• nodes/rest/main.py
• nodes/rest/__init__.py
• records/__init__.py

Any time any of these files is saved/changed on the system, PyLiveDev would shut down the "main" process, re-parse the module looking for imports, and then restart the process.

Note system and pip imports will not be added to the list, like time in the above example. In most cases system files don't change often and it would waste resources to watch them. If you update a pip library, or update python, it's best to shut down PyLiveDev [CRTL-C] and restart it.