Can I force pip to reinstall the current version?

I’ve come across situations where a current version of a package seems not to be working and requires reinstallation. But pip install -U won’t touch a package that is already up-to-date. I see how to force a reinstallation by first uninstalling (with pip uninstall) and then installing, but is there a way to simply force an “update” to a nominally current version in a single step?

Can I use __init__.py to define global variables?

I want to define a constant that should be available in all of the submodules of a package. I’ve thought that the best place would be in in the __init__.py file of the root package. But I don’t know how to do this. Suppose I have a few subpackages and each with several modules. How can I access that variable from these modules?