For maximum performance, Python packages are best installed as zip files. Not all packages, however, are capable of running in compressed form, because they may expect to be able to access either source code or data files as normal operating system files. So, setuptools can install your project as a zipfile or a directory, and its default choice is determined by the project's zip_safe flag.
You can pass a True or False value for the zip_safe argument to the setup() function, or you can omit it. If you omit it, the bdist_egg command will analyze your project's contents to see if it can detect any conditions that would prevent it from working in a zipfile. It will output notices to the console about any such conditions that it finds.
Currently, this analysis is extremely conservative: it will consider the project unsafe if it contains any C extensions or datafiles whatsoever. This does not mean that the project can't or won't work as a zipfile! It just means that the bdist_egg authors aren't yet comfortable asserting that the project will work. If the project contains no C or data files, and does no file or path introspection or source code manipulation, then there is an extremely solid chance the project will work when installed as a zipfile. (And if the project uses pkg_resources for all its data file access, then C extensions and other data files shouldn't be a problem at all. See the Accessing Data Files at Runtime section above for more information.)
However, if bdist_egg can't be sure that your package will work, but you've checked over all the warnings it issued, and you are either satisfied it will work (or if you want to try it for yourself), then you should set zip_safe to True in your setup() call. If it turns out that it doesn't work, you can always change it to False, which will force setuptools to install your project as a directory rather than as a zipfile.
Of course, the end-user can still override either decision, if they are using EasyInstall to install your package. And, if you want to override for testing purposes, you can just run setup.py easy_install --zip-ok . or setup.py easy_install --always-unzip . in your project directory. to install the package as a zipfile or directory, respectively.
In the future, as we gain more experience with different packages and become more satisfied with the robustness of the pkg_resources runtime, the "zip safety" analysis may become less conservative. However, we strongly recommend that you determine for yourself whether your project functions correctly when installed as a zipfile, correct any problems if you can, and then make an explicit declaration of True or False for the zip_safe flag, so that it will not be necessary for bdist_egg or EasyInstall to try to guess whether your project can work as a zipfile.
Should this package be installed with the zip_safe flag set to true?
See here:
http://peak.telecommunity.com/DevCenter/setuptools#setting-the-zip-safe-flag
Note:
For maximum performance, Python packages are best installed as zip files. Not all packages, however, are capable of running in compressed form, because they may expect to be able to access either source code or data files as normal operating system files. So, setuptools can install your project as a zipfile or a directory, and its default choice is determined by the project's zip_safe flag.
You can pass a True or False value for the zip_safe argument to the setup() function, or you can omit it. If you omit it, the bdist_egg command will analyze your project's contents to see if it can detect any conditions that would prevent it from working in a zipfile. It will output notices to the console about any such conditions that it finds.
Currently, this analysis is extremely conservative: it will consider the project unsafe if it contains any C extensions or datafiles whatsoever. This does not mean that the project can't or won't work as a zipfile! It just means that the bdist_egg authors aren't yet comfortable asserting that the project will work. If the project contains no C or data files, and does no file or path introspection or source code manipulation, then there is an extremely solid chance the project will work when installed as a zipfile. (And if the project uses pkg_resources for all its data file access, then C extensions and other data files shouldn't be a problem at all. See the Accessing Data Files at Runtime section above for more information.)
However, if bdist_egg can't be sure that your package will work, but you've checked over all the warnings it issued, and you are either satisfied it will work (or if you want to try it for yourself), then you should set zip_safe to True in your setup() call. If it turns out that it doesn't work, you can always change it to False, which will force setuptools to install your project as a directory rather than as a zipfile.
Of course, the end-user can still override either decision, if they are using EasyInstall to install your package. And, if you want to override for testing purposes, you can just run setup.py easy_install --zip-ok . or setup.py easy_install --always-unzip . in your project directory. to install the package as a zipfile or directory, respectively.
In the future, as we gain more experience with different packages and become more satisfied with the robustness of the pkg_resources runtime, the "zip safety" analysis may become less conservative. However, we strongly recommend that you determine for yourself whether your project functions correctly when installed as a zipfile, correct any problems if you can, and then make an explicit declaration of True or False for the zip_safe flag, so that it will not be necessary for bdist_egg or EasyInstall to try to guess whether your project can work as a zipfile.