How to change prioirty of any process in linux

Use ps -ef | grep .py for searching process id of python processes.
then use top to get an idea about CPU usage for that process.
ps -o pid,comm,nice -p 16024 (where last one is the process id) -> It will return nice value i..e the priority level of the process.
Using this you can change the nice value  renice 10 -p 16024
again analyse using top.
Negative value means high priority (varies from -20 to 19)