[Python-Dev] sys.settrace() in Python 2.3 vs. 2.4 (original) (raw)

Josiah Carlson jcarlson at uci.edu
Fri Jun 30 18:46:55 CEST 2006

I've previously asked on python-list, but have recieved no responses or explanations. Maybe someone here with a better memory can help, and I apologize for asking a somewhat off-topic question about such an archaic version of Python.

According to my reading of Python 2.3 docs, the call to goo() should exit with a KeyboardInterrupt...

import sys

def goo():
    while 1:
        pass

count = [100]
def foo(frame, event, arg):
    count[0] -= 1
    if not count[0]:
        raise KeyboardInterrupt
    return foo

sys.settrace(foo)

goo()

In Python 2.3, the above call to goo() doesn't return. Adding print statements suggests that foo() is only called for each line executed in goo() once. It exits with a KeyboardInterrupt in 2.4, as expected, where foo() is called for essentially every operaition performed. Does anyone have an idea why this is the case? I've checked the release notes for both 2.3 and 2.4 and found no discussion of trace functions in them or in sourceforge (I could be entering the wrong search terms, of course).

Any pointers as to why there is a difference would be appreciated. Thank you,

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