What components do you use to do TDD with Python?

I prefer pytest over unittest. The pros are:

• you can write tests as functions (you can also use methods in classes like in unittest)
• the conftest.py mechanism allows you to group setups that are evaluated only at necessity in a cascading fashion in sub folders
• the test function explicitly declares what mocks it needs to run
• fixtures make a great way to organize tests that need a complex setup and tests that can run super fast and have initializers that can be run per session, per test, per file/module
• there are no custom assertion methods (you use mostly assert and with)
• it's unittest compatible
• it has lots of plugins

the cons are:

• it requires a little bit of time to understand how fixtures work
• it's one more package to install

I don’t practice TDD, but for testing python I’ve been using unittest along with MyPy. MyPy is a huge help in writing good working code and I can’t recommend it enough. It’s very very very far from perfect but it’s also light years ahead of the frustrating buggy mess of trying to write completely untyped code.