import sys


def trace_func(frame, event, arg):
    value = frame.f_locals["a"]
    if value % 2 == 0:
        value += 1
        frame.f_locals["a"] = value


def f(a):
    print(a)


if __name__ == "__main__":
    trace = sys.gettrace()
    sys.settrace(trace_func)
    for i in range(0, 5):
        f(i)
    sys.settrace(trace)