If you store the version in a python file like this, you don't have to read it in this way.
I would suggest either putting the version string in __init__.py and then just import the package, e.g.

    from doctool import __version__

But in this case, where the project is really rather small, and it's easy to forget to bump the version, It could be a better idea to get the version specified in setup.py by doing something along these lines:

    import pkg_resources
    version = pkg_resources.require("doctool")[0].version