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apipkg: namespace control and lazy-import mechanism

Project description

Welcome to apipkg !

With apipkg you can control the exported namespace of a Python package and greatly reduce the number of imports for your users. It is a small pure Python module that works on CPython 3.7+, Jython and PyPy. It cooperates well with Python’s help() system, custom importers (PEP302) and common command-line completion tools.

Usage is very simple: you can require ‘apipkg’ as a dependency or you can copy paste the ~200 lines of code into your project.

Tutorial example

Here is a simple mypkg package that specifies one namespace and exports two objects imported from different modules:

# mypkg/
import apipkg
apipkg.initpkg(__name__, {
    'path': {
        'Class1': "_mypkg.somemodule:Class1",
        'clsattr': "_mypkg.othermodule:Class2.attr",

The package is initialized with a dictionary as namespace.

You need to create a _mypkg package with a and containing the respective classes. The _mypkg is not special - it’s a completely regular Python package.

Namespace dictionaries contain name: value mappings where the value may be another namespace dictionary or a string specifying an import location. On accessing an namespace attribute an import will be performed:

>>> import mypkg
>>> mypkg.path
<ApiModule 'mypkg.path'>
>>> mypkg.path.Class1   # '_mypkg.somemodule' gets imported now
<class _mypkg.somemodule.Class1 at 0xb7d428fc>
>>> mypkg.path.clsattr  # '_mypkg.othermodule' gets imported now
4 # the value of _mypkg.othermodule.Class2.attr

The mypkg.path namespace and its two entries are loaded when they are accessed. This means:

  • lazy loading - only what is actually needed is ever loaded

  • only the root “mypkg” ever needs to be imported to get access to the complete functionality

  • the underlying modules are also accessible, for example:

from mypkg.sub import Class1

Including apipkg in your package

If you don’t want to add an apipkg dependency to your package you can copy the file somewhere to your own package, for example _mypkg/ in the above example. You then import the initpkg function from that new place and are good to go.


If you have questions you are welcome to

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