https://github.com/brettlangdon/importhook

Python package for executing functions when packages are imported
https://github.com/brettlangdon/importhook

hooks import module python python3

Last synced: 2 months ago
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Python package for executing functions when packages are imported

• Host: GitHub
• URL: https://github.com/brettlangdon/importhook
• Owner: brettlangdon
• License: mit
• Created: 2018-08-24T11:50:49.000Z (over 6 years ago)
• Default Branch: master
• Last Pushed: 2023-04-14T22:22:00.000Z (over 1 year ago)
• Last Synced: 2024-10-12T22:44:43.758Z (3 months ago)
• Topics: hooks, import, module, python, python3
• Language: JavaScript
• Homepage: https://brettlangdon.github.io/importhook/
• Size: 198 KB
• Stars: 25
• Watchers: 4
• Forks: 4
• Open Issues: 4
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG
  • License: LICENSE

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README

        
Importhook

=========

[![PyPI version](https://badge.fury.io/py/importhook.svg)](https://badge.fury.io/py/importhook)

`importhook` is a Python package that lets you configure functions to call whenever a specific module is imported.

## Installation

```bash

pip install importhook

```

## Usage

Configure a hook to be called when `socket` module is imported.

```python

import importhook

# Setup hook to be called any time the `socket` module is imported and loaded into module cache

@importhook.on_import('socket')

def on_socket_import(socket):

    print('"socket" module has been imported')

# Import module

import socket

```

You can also use `importhook` to intercept and modify a module on import by returning a Python module from your hook function.

```python

import importhook

# Setup hook to be called any time the `socket` module is imported and loaded into module cache

@importhook.on_import('socket')

def on_socket_import(socket):

    new_socket = importhook.copy_module(socket)

    setattr(new_socket, 'gethostname', lambda: 'patched-hostname')

    return new_socket

# Import module

import socket

# Prints: 'patched-hostname'

print(socket.gethostname())

```

`importhook` also comes with helpers to reload modules that have already been imported.

```python

import socket

import importhook

# Setup hook to be called any time the `socket` module is imported and loaded into module cache

# DEV: `on_socket_import` will be called immediately because the `socket` module is already loaded

@importhook.on_import('socket')

def on_socket_import(socket):

    print('"socket" module has been imported')

# Reload the socket module

# DEV: Reassign to `socket` in case one of our hooks modifies the module

socket = importhook.reload_module(socket)

```

## Design decisions

### Overwriting sys.meta_path

If a Python developer wants to modify the import behavior they can do so by adding a new `importlib.abc.Finder`

class into `sys.meta_path`.

```python

import sys

# Add our custom `importlib.abc.Finder` to `sys.meta_path`

sys.meta_path.append(MyCustomFinder)

```

One of the major design decisions we have taken with `importhook` is to wrap/overwrite `sys.meta_path`.

What it means is that `importhook` will continue to work as expected regardless of any other modifications of `sys.meta_path`.

There is however one caveat, if you were to do `sys.meta_path = [MyCustomFinder] + sys.meta_path` then `sys.meta_path` will get

converted back into a `list`. Existing modifications to the finders in `sys.meta_path` will still work as expected, but any

new finders added will not get hooked.