Testing/Automated testing | Quality Assurance in Python

I recently took up a goal to learn Q/A (specifically browsers and web technology) and would like to ask for an advice from You, Python gurus. I came up with a list of questions.

1. What are the modules you need to know? (list of modules)
2. What Python tools do you use/are the best? (list of tools)
3. Few things one should be aware when : write/review test cases & execute/analyze tests

Thank you all.