How to trace function entries and exits in Python without using decorators. Excerpt from: http://blog.dscpl.com.au/2014/02/performance-overhead-of-using-decorators.html

python-tracing-howto.md

In order to trace the execution of our code we can use Python's profile hooks mechanism.

import sys 

def tracer(frame, event, arg):
    print(frame.f_code.co_name, event) 

sys.setprofile(tracer) 

call_something(...)

The purpose of the profile hook is to allow you to register a callback function which is called on the entry and exit of all functions. Using this was can trace the sequence of function calls that are being made.