itrace.py 文件源码

def start():
    """
    Start call tracing.
    """
    global _trace_calls
    if sys.getprofile() is not None:
        raise RuntimeError("another profile function is already active.")
    if _trace_calls is None:
        raise RuntimeError("trace.setup() was not called before trace.start().")
    sys.setprofile(_trace_calls)