subprocess.py 文件源码

def wait(self, timeout=None, endtime=None):
            """Wait for child process to terminate.  Returns returncode
            attribute."""
            if self.returncode is not None:
                return self.returncode

            # endtime is preferred to timeout.  timeout is only used for
            # printing.
            if endtime is not None or timeout is not None:
                if endtime is None:
                    endtime = _time() + timeout
                elif timeout is None:
                    timeout = self._remaining_time(endtime)

            if endtime is not None:
                # Enter a busy loop if we have a timeout.  This busy loop was
                # cribbed from Lib/threading.py in Thread.wait() at r71065.
                delay = 0.0005 # 500 us -> initial delay of 1 ms
                while True:
                    (pid, sts) = self._try_wait(os.WNOHANG)
                    assert pid == self.pid or pid == 0
                    if pid == self.pid:
                        self._handle_exitstatus(sts)
                        break
                    remaining = self._remaining_time(endtime)
                    if remaining <= 0:
                        raise TimeoutExpired(self.args, timeout)
                    delay = min(delay * 2, remaining, .05)
                    time.sleep(delay)
            else:
                while self.returncode is None:
                    (pid, sts) = self._try_wait(0)
                    # Check the pid and loop as waitpid has been known to return
                    # 0 even without WNOHANG in odd situations.  issue14396.
                    if pid == self.pid:
                        self._handle_exitstatus(sts)
            return self.returncode