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Adrian Georgescu, 05/27/2013 05:48 pm

Building a Python Framework to bundle inside Blink

In order to avoid using the system Python a custom Framework build is needed. Using a bundled Python version will make the package bigger in size, but all package versions are controlled and not up to the environment. Also, we can use the latest Python version, with latest bugfixes and features, since Apple only updates the system Python version on every major OS release.

Setting default Python interpreter on OSX for 32 bits

defaults write com.apple.versioner.python Version 2.7
export VERSIONER_PYTHON_PREFER_32_BIT=yes

Building the Python Framework itself

  • Download the desired Python version, at the time of this writing, 2.7.5
wget http://python.org/ftp/python/2.7.5/Python-2.7.5.tar.bz2
  • Uncompress and get ready to compile
tar jxvf Python-2.7.5.tar.bz2
cd Python-2.7.5
  • Create a temporary directory for the build result
mkdir -p /tmp/py
  • Compile Python (Framework build) in 32 bits mode and with compatibility for OSX >= 10.6
./configure --prefix=/tmp/py --enable-framework=/tmp/py MACOSX_DEPLOYMENT_TARGET=10.6 ARCHFLAGS="-arch i386" CFLAGS="-arch i386" CXXFLAGS="-arch i386" LDFLAGS="-arch i386" 
make
make install

The resulting framework will be located in /tmp/py

  • Change the dynamic link target in the main binary file of the Python Framework
cd /tmp/py/Python.framework/Versions/2.7
chmod +w Python
install_name_tool -id @executable_path/../Frameworks/Python.framework/Versions/2.7/Python Python
chmod -w Python

The framework is almos ready for inclusion on the project.

NOTE: Be careful when copying the framework around, it contains symlinks and if cp -r is used the size will we doubled, use cp -RH instead.

  • Reduce the size of the Python Framework:

There are a number of things that can be removed from the framework directory to make it smaller in size:

*.pyc
*.pyo
Versions/Current/Mac
Versions/Current/bin
Versions/Current/share
Versions/Current/Resources/English*
Versions/Current/Resources/*.app
Versions/Current/lib/python2.7/test
Versions/Current/lib/python2.7/plat-*
Versions/Current/lib/python2.7/idlelib
Versions/Current/lib/python2.7/curses
Versions/Current/lib/python2.7/lib2to3
Versions/Current/lib/python2.7/lib-tk
Versions/Current/lib/python2.7/bsddb
  • Prevent system paths from being used with this bundle

Edit Versions/Current/lib/python2.7/site.py and add the following lines at the end on the main() function body:

    # Remove system paths so that only things contained in this Framework are used
    sys.path = [x for x in sys.path if not x.startswith(('/System', '/Library'))]

Compiling PyObjC

In order to get a PyObjC version that will work with the framework created above (Python 2.7, 32 bits) an equivalent Python must be used to compile it. That is, if has to be a Python 2.7 version (it doesn't have to be the exact version) and it has to be a 32 bit version or the ARCHFLAGS env variable must be set to "-arch i386". The MACOSX_DEPLOYMENT_TARGET must also be set to the appropriate value.

PyObjcC can be installed with easy_install or pip. We install it in 2 steps to save some compilation time due to a bug in the build system:

pip install pyobjc-core
pip install pyobjc

When compiling PyObjC a Python package will be created for every system framework, but not all of them are needed (at the moment), so just pick the ones we use:

AddressBook
AppKit
Cocoa
CoreFoundation
Foundation
LaunchServices
PyObjCTools
Quartz
QTKit
WebKit
objc

NOTE: The objc package is located inside a PyObjC directory, just copy it from there, without the parent directory.

Building lxml

Building lxml can be a huge pain. Here is the only way I managed to compile a version which works, not the latest though:

wget https://pypi.python.org/packages/source/l/lxml/lxml-2.3.6.tar.gz
tar zxvf lxml-2.3.6.tar.gz
cd lxml-2.3.6

export CC="gcc" 
export ARCHFLAGS="-arch i386" 
export CFLAGS="-arch i386" 

python setup.py build --static-deps --libxml2-version=2.7.8 --libxslt-version=1.1.24
python setup.py install

Building python-ldap

The only version known to work with OSX 10.6 and up is 2.3.13, so that one should be installed:

pip install python-ldap==2.3.13