Why does easy_install extract some python eggs and not others?

Question

Looking in my /usr/local/lib/python.../dist-package directory, I have .egg directories and .egg files.

Why does the installer choose to extra packages to the .egg directory, yet leave other files with .egg extensions?

Answer 1

I can't explain why some eggs are zipped (the files) and some are directories, but I can offer this: if you hate zipped eggs (like I do) put this in the [easy_install] section of your ~/.pydistutils.cfg:

zip_ok = false

Answer 2

If the package contains only pure-Python code, it can stay as just an egg file. The Python interpreter can load the Python modules directly from the egg. If the package contains modules written in C or other data, then egg needs to be extracted so the C modules and/or data can be accessed. That's the default behavior of packages, I believe. Newer versions of Python might be able to load C modules from egg files; I'm not sure about that part.

The creator of the package can also specifically instruct the installer to unzip the package, by passing zip_safe = False to setup() in their setup.py.

Finally, the person doing the installing can tell easy_install explicitly to unpack eggs by passing it the -Z option or by setting zip_ok = false in the pydistutils.cfg.