Installing Python Imaging Library (PIL) under virtualenv or buildout

I have greatly struggled to have PIL library support in isolated Python environments like virtualenv –no-site-packages.

For example, when installing Satchmo shop under virtualenv:

../bin/clonesatchmo.pyhe Python Imaging Library is not installed. Install from your distribution binaries.

../bin/clonesatchmo.py
The Python Imaging Library is not installed. Install from your distribution binaries.

Though it clearly is there, installed by easy_install PIL command:

ls ../lib/python2.5/site-packages/PIL-1.1.7-py2.5-linux-x86_64.egg
ArgImagePlugin.py	 ExifTags.py		  GimpGradientFile.pyc...

Does anyone know if this problem is with PIL itself, eggified PIL or something else?

In any case, there is an easy workaround: use system-wide PIL (sudo apt-get install python-imaging) and symlink PIL from your site-wide installation under the isolated Python environment:

(satchmo-py25)mulli% pwd
/srv/plone/mmaspecial/satchmo-py25/lib/python2.5/site-packages
(satchmo-py25)mulli% ln -s /usr/lib/python2.4/PIL .

Mysterious buildout error – missing docs/HISTORY.txt file

I was getting the following error with Plone buildout

…

Develop: '/home/moo/workspace/collective.easytemplate'
Traceback (most recent call last):
  File "/tmp/tmp_G8621", line 11, in ?
  File "/usr/lib/python2.4/site-packages/setuptools/command/easy_install.py", line 655, in install_eggs
    return self.build_and_install(setup_script, setup_base)
  File "/usr/lib/python2.4/site-packages/setuptools/command/easy_install.py", line 931, in build_and_install
    self.run_setup(setup_script, setup_base, args)
  File "/usr/lib/python2.4/site-packages/setuptools/command/easy_install.py", line 919, in run_setup
    run_setup(setup_script, args)
  File "/usr/lib/python2.4/site-packages/setuptools/sandbox.py", line 26, in run_setup
    DirectorySandbox(setup_dir).run(
  File "/usr/lib/python2.4/site-packages/setuptools/sandbox.py", line 63, in run
    return func()
  File "/usr/lib/python2.4/site-packages/setuptools/sandbox.py", line 29, in <lambda>
    {'__file__':setup_script, '__name__':'__main__'}
  File "setup.py", line 9, in ?
    return open(os.path.join(os.path.dirname(__file__), *rnames)).read()
  File "/usr/lib/python2.4/site-packages/setuptools/sandbox.py", line 166, in _open
    return _open(path,mode,*args,**kw)
IOError: [Errno 2] No such file or directory: 'docs/HISTORY.txt'
An internal error occured due to a bug in either zc.buildout or in a
recipe being used:
Traceback (most recent call last):
  File "/home/moo/workspace/Plone-3.1/eggs/zc.buildout-1.1.1-py2.4.egg/zc/buildout/buildout.py", line 1477, in main
    getattr(buildout, command)(args)
  File "/home/moo/workspace/Plone-3.1/eggs/zc.buildout-1.1.1-py2.4.egg/zc/buildout/buildout.py", line 324, in install
    installed_develop_eggs = self._develop()
  File "/home/moo/workspace/Plone-3.1/eggs/zc.buildout-1.1.1-py2.4.egg/zc/buildout/buildout.py", line 556, in _develop
    zc.buildout.easy_install.develop(setup, dest)
  File "/home/moo/workspace/Plone-3.1/eggs/zc.buildout-1.1.1-py2.4.egg/zc/buildout/easy_install.py", line 868, in develop
    assert os.spawnl(os.P_WAIT, executable, _safe_arg (executable), *args) == 0
AssertionError

My product had docs folder. HISTORY.txt was there properly. This made me scratch my head for a while.

Buildout calls easy_install as an external process. If easy_install eggs have dependencies in their setup.py easy_install tries to download and install these eggs.

There is no reported progress what eggs are installed in easy_install process created from buildout. Looks like buildout verbosity (-v) switch does not reach easy_install.

So the problem was not in my product, but in its dependency. However the debug output did not reveal that we were dealing with a dependency. Is there easy means to solve this kind of problems? I bluntly put debug prints inside my server wide setuptools Python files to known which was the faulty dependency.

It turned out that easy_install was trying to execute setup.py against a downloaded source distribution (.tar.gz). I had the same egg as a local source code copy. The source code contains docs folder, the egg doesn’t.

The solution was to change buildout.cfg develop directive to be the same as the flattened dependency order of the eggs (dependencies come top). This way setup.py was evaluated correctly against the source code folder.

Python code management & deployment – a glance at zc.buildout and few others

We’ve been using zc.buildout for Plone deployment and it’s working out great. A few days ago implemented a buildout recipe for Django project deployment, automatic web configuration, symlinking, media-folder structuring etc. and while I got it working, I came up with twisted feelings.

Buildout is from the creators of Zope (I suppose) so you can expect a powerful project code management tool. The question is, however, whether or not it suits your needs. In my case I found out it too heavy. I mean, to add even a simple task you have to create a new “recipe” (a package) that does the tricks. Of course some recipes are generic (found from PyPi) and you can just run them with your own INI options, but in my case I had to do some custom implementation. Creating a new python package isn’t that hard for sure but there’s of course some learning curve, so the real question is should you spend time to learn it or not?

I found out that zc.buildout has some nice features like:

• Automatic requirements processing through setuptools
• Automatic (yet simple) removal of directories during recipe uninstall
• Clear structure (install(), update() & uninstall() methods)
• INI-syntax, python does have a clear syntax but INI is always clearer for a newbie
• Easy script creation (adjust python paths somewhat automatically)
• Easily repeatable
• Passing of arguments from one recipe to another
• etc.

The problems?

• It takes a while to learn zc.buildout
• It takes ‘another while’ to learn to write recipes
• Too much hassle for little things
• INI-syntax is very limited in features
• Buildout easily updates all your packages (that means also the ones you didn’t want to!)
• Lack of documentation (it has good docs to get you going.. but after a while it leaves you with open questions)
• Unnecessary overhead (for each script you launch, you’ll need a launcher script created via buildout)

There’s no denying zc.buildout is powerful, but I wouldn’t use it for projects which need reasonable amount of customization. It’s just plain easier and quicker to write shell scripts and while those won’t provide you with any sort of ready tools you won’t propably need them. For bringing up somewhat static environment, where you don’t need to hack things (like that for Plone) it’s quite a decent option, however.

I also explored alternatives to zc.buildout. I’ve been reading about earlier virtualenv but haven’t really tried it out until now. It looks very promising and creates a more flexible environment compared to zc.buildout. Of course their goals are not exactly the same. Also, there are a few other alternatives out there, among them a new Python code management tool called Paver (just look at that cool logo.. it does remind you of Indiana Jones, does it not?). I glanced through the Paver docs and it looks like it might be the way to go (Paver also supports virtualenv), but didn’t quite get the grasp of the benefits just yet. Anyway, if you are still interested in code management and deployment, I’d recommend you to read the Paver release announcement and also Paver forewords. They should clear things up.