How do I get all the latest transactions from Bitcoin network using Python? Is there a Python client to listen to all latest transaction from the Bitcoin network? How does blockchain.info doing it?
Blockchain.info uses a special system that doesn't involve Python (as far as we know), they're most likely using a modifed node that notifies them of transactions.

The easy way

Just use Blockchain.info's transaction notification service. Their websockets api lets anyone subscribe to any bitcoin address.

The hard way

If you want to listen to all latest transactions, and not to addresses you own, you're going to need more in depth control. Otherwise use Bitcoind and its walletnotify parameter. Check out PyNode, a Bitcoin node implementation in Python.