loop.py

#!/usr/bin/env python3

import sys
import time

def foo():
    print('ni')
    time.sleep(0.1)
    pass

def tracefunc(frame, event, arg, indent=[0]):
    if event == 'line' and frame.f_lineno >= 9:
        frame.f_lineno = 7
    return tracefunc

sys.settrace(tracefunc)
foo()