import sys

def tracefunc(*args):
    print 'in tracefunc', repr(args)
    return tracefunc
    
def bar():
    print 'bar'
    
def foo():
    sys.settrace(tracefunc)
    print 'foo'
    bar()
    if '--reset-tracing' in sys.argv:
        sys.settrace(None)
    
try:
    import stackless
except ImportError:
    stackless = None
    
if stackless:
    stackless.tasklet(foo)()
    stackless.schedule()
else:
    foo()