Source function resolving poisson's equation

Hello everyone, I am new with FEniCS, and I am struggling to understand everything. I am trying to solve poisson’s equation, but my function source f is a python function and not an expression. And I do not know how to transform it to be compiled in C++. This my code, and the error I had.
Thanks for your help!

Hi, see for instance: How to define source term function . And for later problems, please post a Minimal Working example as described here: Read before posting: How do I get my question answered?