subprocess.py 文件源码

def _internal_poll(self, _deadstate=None, _waitpid=os.waitpid,
                _WNOHANG=os.WNOHANG, _os_error=os.error, _ECHILD=errno.ECHILD):
            """Check if child process has terminated.  Returns returncode
            attribute.

            This method is called by __del__, so it cannot reference anything
            outside of the local scope (nor can any methods it calls).

            """
            if self.returncode is None:
                try:
                    pid, sts = _waitpid(self.pid, _WNOHANG)
                    if pid == self.pid:
                        self._handle_exitstatus(sts)
                except _os_error as e:
                    if _deadstate is not None:
                        self.returncode = _deadstate
                    if e.errno == _ECHILD:
                        # This happens if SIGCLD is set to be ignored or
                        # waiting for child processes has otherwise been
                        # disabled for our process.  This child is dead, we
                        # can't get the status.
                        # http://bugs.python.org/issue15756
                        self.returncode = 0
            return self.returncode