threading.py debug基类

_VERBOSE = False

if __debug__:

    class _Verbose(object):

        def __init__(self, verbose=None):
            if verbose is None:
                verbose = _VERBOSE
            self.__verbose = verbose

        def _note(self, format, *args):
            if self.__verbose:
                format = format % args
                # Issue #4188: calling current_thread() can incur an infinite
                # recursion if it has to create a DummyThread on the fly.
                ident = _get_ident()
                try:
                    name = _active[ident].name
                except KeyError:
                    name = "<OS thread %d>" % ident
                format = "%s: %s\n" % (name, format)
                _sys.stderr.write(format)

else:
    # Disable this when using "python -O"
    class _Verbose(object):
        def __init__(self, verbose=None):
            pass
        def _note(self, *args):
            pass

查看threading.py脚本时看到_RLock, _Condition等类皆继承_Verbose,其目的是为了输入调试信息。python -O为关闭调试输出