I don't know how to mine blocks with Python. Can I mine blocks with Pyethapp?
I haven't used it myself, so others may want to comment further.
From the documentation,
pyethapp is composed of
pydevp2p, the former of which:
pyethereum - the core library, featuring the blockchain, the ethereum virtual machine, mining
So in answer to your question:
Can I mine blocks with Pyethapp?
I'd say the answer is "yes".
If you're open to an Alpha-level project still in active development, then you might also be interested in py-evm.
Py-EVM is a new implementation of the Ethereum Virtual Machine written in python. It is currently in active development but is quickly progressing through the test suite provided by ethereum/tests ... Development will focus on creating an EVM with a well defined API, friendly and easy to digest documentation which can be run as a fully functional mainnet node.