SIP
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 SIPBuilder
and SIPPackage
base classes come with the following phases:
configure
- configure the packagebuild
- build the packageinstall
- 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()
[
'PyQt5', 'PyQt5.QtCore', 'PyQt5.QtGui', 'PyQt5.QtHelp',
'PyQt5.QtMultimedia', 'PyQt5.QtMultimediaWidgets', 'PyQt5.QtNetwork',
'PyQt5.QtOpenGL', 'PyQt5.QtPrintSupport', 'PyQt5.QtQml',
'PyQt5.QtQuick', 'PyQt5.QtSvg', 'PyQt5.QtTest', 'PyQt5.QtWebChannel',
'PyQt5.QtWebSockets', 'PyQt5.QtWidgets', 'PyQt5.QtXml',
'PyQt5.QtXmlPatterns'
]
Large, complex packages like py-pyqt5
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.
The SIPPackage
base class automatically detects these module
names for you. If, for whatever reason, the module names detected
are wrong, you can provide the names yourself by overriding
import_modules
like so:
import_modules = ['PyQt5']
These tests often catch missing dependencies and non-RPATHed libraries. Make sure not to add modules/packages containing the word “test”, as these likely won’t end up in the installation directory, or may require test dependencies like pytest to be installed.
These tests can be triggered by running spack install --test=root
or by running spack test run
after the installation has finished.
External documentation
For more information on the SIP build system, see: