imphook 0.1

Simple and clear import hooks for Python - import anything as if it were a Python module

The imphook module allows to easily define per file type import hooks, i.e. overload or extend import processing for particular file types, without affecting processing of other file types, and at the same time, while ensuring that new processing integrates as seamlessly as possible with normal Python import rules.

Besides the Python-level API to install import hooks, the module also provides command-line interface to run an existing Python script or module with one or more import hooks preloaded (i.e. without modifying existing script source code).

Some but not all things you can easily do using imphook (most of these require additional modules to do the heavy lifting, imphook just allows to plug it seamlessly into the Python import system):

• Override importing of (all or some) .py files, to support new syntax or semantics in them.

• Import files written using a DSL (domain-specific language) as if they were Python modules. E.g., config or data files.

• Import modules written in other language(s), assuming you have an interpreter(s) for them.

• Import binary files, e.g. Java or LLVM bytecode.

imphook works both with new, lightweight legacy-free Python API, as promoted by the Pycopy Python dialect (the original source of the “easy import hooks” idea), and CPython (the older, reference Python implementation), and with other Python implementations which are CPython-compatible.

Quick Start

Make sure that you already installed imphook using:

pip3 install -U imphook

Below is a complete example of an import hook module to load key = value style config files:

import imphook

def hook(filename):
    with open(filename) as f:
        # Create a module object which will be the result of import.
        mod = type(imphook)("")
        for l in f:
            k, v = [x.strip() for x in l.split("=", 1)]
            setattr(mod, k, v)
        return mod

imphook.add_import_hook(hook, (".conf",))

Save this as the mod_conf.py file, and add the two following files to test it:

example_settings.conf:

var1 = 123
var2 = hello

example_conf.py:

import example_settings as settings

print(settings.var1)
print(settings.var2)

Now run:

python3 -m imphook -i mod_conf example_conf.py

As you can see, the example_conf.py is able to import example_settings.conf as if it were a normal Python module.

Besides copy-pasting the above and other examples, you can also clone the Git repository of imphook, which contains various ready-to-use examples:

git clone https://github.com/pfalcon/python-imphook