How to handle different versions of python protobu

问题:

My python package contains a lot of files compiled by python-protobuf (python2-protobuf-2.5.0 on Arch Linux), I installed the package on Ubuntu server 12.04.3 (which have python-protobuf-2.4.1), tried to run the code, and hit the following error:

from google.protobuf.internal import enum_type_wrapper
ImportError: cannot import name enum_type_wrapper

I think it's because the protobuf modules in my package are compiled by protobuf-2.5.0 and they do not work with protobuf-2.4.1.

I have no idea of the environments in which my code may run, the version of protobuf may vary. How to make my package work with both protobuf 2.4 and 2.5?

(A possible way: include two different sets of protobuf libraries (one compiled by 2.4.1, the other compiled by 2.5.0) in my package, get google.protobuf version at runtime and select the protobuf libraries to import. Is it possible?

回答1:

You need to specify the version of protobuf that will work with in your setup.py in the list install_requires=['protobuf>=2.5.0']. With a Python package, you can put just the name or the exact versions that will run with the package using ==. I believe you can also specify != for specific versions.

If you are not packaging it with a setup.py, you should set up a virtualenv and put a file install_requires.txt with all the specific python packages and versions in the root of the project.

That might look like:

$ cd ../project
$ virtualenv project_venv
$ source project_venv/bin/activate
$ cd project
$ pip install protobuf>=2.5.0
$ pip freeze > ./requirements.txt

Then someone you distribute to can activate their virtualenv and do:

$ pip install -r requirements.txt

Make sure your package will work from a fresh virtualenv by installing with that method. This is also good to check before installing via a setup.py. You want to make sure your requirements will get anyone working who just does a fresh sudo python setup.py install, or python setup.py install in a virtualenv context.

You can exit a virtualenv context with:

$ deactivate

回答2:

Your best bet may be to include a copy of the protobuf runtime library with your package, maybe under a different package name. Then you can make sure that it matches the version of your generated code.

Another option is to invoke protoc as part of the installation process, so you get whatever version is available on the host.

I don't think packaging multiple versions of your generated code sounds like a good idea -- you'll just have problems again when the next protobuf release comes out.