capture.py 文件源码

def __init__(self, targetfd, tmpfile=None):
        self.targetfd = targetfd
        try:
            self.targetfd_save = os.dup(self.targetfd)
        except OSError:
            self.start = lambda: None
            self.done = lambda: None
        else:
            if targetfd == 0:
                assert not tmpfile, "cannot set tmpfile with stdin"
                tmpfile = open(os.devnull, "r")
                self.syscapture = SysCapture(targetfd)
            else:
                if tmpfile is None:
                    f = TemporaryFile()
                    with f:
                        tmpfile = safe_text_dupfile(f, mode="wb+")
                if targetfd in patchsysdict:
                    self.syscapture = SysCapture(targetfd, tmpfile)
                else:
                    self.syscapture = NoCapture()
            self.tmpfile = tmpfile
            self.tmpfile_fd = tmpfile.fileno()