Python Hot Module Reload

Better debugging experience with HMR

Automatic reload your project when files are modified.

No need to modify your source code. Works in any environment.

Supported Syntax:

• ✅ import X
• ✅ from X import Y

Supported Types:

• ✅ Module
• ✅ Function
• ✅ Class

Installation

pip install python-hmr

Quick Start

Caution

From v0.3.0, there is only one API, hmr.reload.

Import your dev packages as usual. And add 2 lines for automatically reloading.

import dev

import hmr
dev = hmr.reload(dev)

If you have multiple modules to reload, you can do it like this.

from dev import run1, run2

import hmr
run1, run2 = hmr.reload(run1, run2)

Now you are ready to go! Try to modify the run1 or run2 and see the magic happen.

Detailed Usage

Function/Class instance

When you try to add HMR for a function or class, remember to pass the name of the function or class instance without parenthesis.

from dev import Runner

import hmr
Runner = hmr.reload(Runner)

a = Runner()
b = Runner()

Important

Here, when both a and b will be updated after reloading. This may be helpful if you have an expansive state store within the class instance.

However, it's suggested to reinitialize the class instance after reloading.

@Decorated Function

Use functools.wraps to preserve signature of your function, or the function information will be replaced by the decorator itself.

import functools

def work(f):
    @functools.wraps(f)
    def args(*arg, **kwargs):
        return f(*arg, **kwargs)

    return args

Stateful application

If your application is stateful, you can exclude the state from being reloaded. For simplicity, you can group all your state variable into the same .py file like state.py and exclude that from being reloaded.

Make sure you know what you are doing. This could lead to unexpected behavior and unreproducible bugs.

import dev

import hmr
dev = hmr.reload(dev, exclude=["dev.state"])

In this way dev/state.py will not be reloaded, the state will persist.

This also apply when reloading a function or class.

from dev import run

import hmr
run = hmr.reload(run, exclude=["dev.state"])

Acknowledgement

Inspired from the following package.

• auto-reloader
• reloadr