Is there a nice way to set directory/project local environment variables?

I have been working on several projects and they require different environment variables (e.g., PATH for different versions of clang executables, PYTHONPATH for several external modules). Whenever I work on one project, I have to modify these environment myself (e.g., change .zshrc/.bashrc and source it); and I sometimes forgot it and made the mistake.

Is there a way/project that helps do this automatically, similar to what virtualenv does in Python?