For the database I will use MySQL and SQLAlchemy, and Twisted for the network. If you know any interesting library which can help me doing this thing, tell me please. That is, if you don't mind it.
The philosophy of Python's standard libraries is "batteries included", so pretty much everything you'll need exists in the standard lib (apart from things like Twisted and SQLAlchemy). So it depends on what you want to do. Google is your friend in this case. If you want to do some particular thing in your code, just search "python <particular thing>". This will tell you pretty quickly if there is a package in the standard lib to help you with this.
It would be pointless to suggest particular libraries with knowing exactly what you're building. However, being rather passionate about Python, I will suggest a few other subjects for further reading:
- Python style guide (PEP8) - http://www.python.org/dev/peps/pep-0008/ <--- read this twice
- pep8 tool (for automatically checking if your code meets style guidelines) - https://pypi.python.org/pypi/pep8
- Learn about unit testing and write tests for your code - http://docs.python.org/2/library/unittest.html
- From a command prompt, type this: python -c "import this". Read.