SIPPackage

SIP is a tool that makes it very easy to create Python bindings for C and C++ libraries. It was originally developed to create PyQt, the Python bindings for the Qt toolkit, but can be used to create bindings for any C or C++ library.

SIP comprises a code generator and a Python module. The code generator processes a set of specification files and generates C or C++ code which is then compiled to create the bindings extension module. The SIP Python module provides support functions to the automatically generated code.

Phases

The SIPPackage base class comes with the following phases:

  1. configure - configure the package

  2. build - build the package

  3. install - install the package

By default, these phases run:

$ python configure.py --bindir ... --destdir ...
$ make
$ make install

Important files

Each SIP package comes with a custom configure.py build script, written in Python. This script contains instructions to build the project.

Build system dependencies

SIPPackage requires several dependencies. Python is needed to run the configure.py build script, and to run the resulting Python libraries. Qt is needed to provide the qmake command. SIP is also needed to build the package. All of these dependencies are automatically added via the base class

extends('python')

depends_on('qt', type='build')
depends_on('py-sip', type='build')

Passing arguments to configure.py

Each phase comes with a <phase_args> function that can be used to pass arguments to that particular phase. For example, if you need to pass arguments to the configure phase, you can use:

def configure_args(self, spec, prefix):
    return ['--no-python-dbus']

A list of valid options can be found by running python configure.py --help.

Testing

Just because a package successfully built does not mean that it built correctly. The most reliable test of whether or not the package was correctly installed is to attempt to import all of the modules that get installed. To get a list of modules, run the following command in the site-packages directory:

$ python
>>> import setuptools
>>> setuptools.find_packages()
['QtPy5']

Large, complex packages like QtPy5 will return a long list of packages, while other packages may return an empty list. These packages only install a single foo.py file. In Python packaging lingo, a “package” is a directory containing files like:

foo/__init__.py
foo/bar.py
foo/baz.py

whereas a “module” is a single Python file. Since find_packages only returns packages, you’ll have to determine the correct module names yourself. You can now add these packages and modules to the package like so:

import_modules = ['PyQt5']

When you run spack install --test=root py-pyqt5, Spack will attempt to import the PyQt5 module after installation.

These tests most often catch missing dependencies and non-RPATHed libraries.