相关疑难解决方法(0)

是否有一个参考某处确定何时用括号括起元组是否需要？

这是最近让我感到惊讶的一个例子:

>>> d = {}
>>> d[0,] = 'potato'
>>> if 0, in d:
  File "<stdin>", line 1
    if 0, in d:
        ^
SyntaxError: invalid syntax

我希望变量output_format是一个字符串.但是当我运行脚本时,它给了我一个tuple类型并抛出异常.

如果我在Python解释器中运行,它给了我一个预期的字符串.

('--sout "#standard{access=file,vcodec=h264,dst=c0_s0_h264_640x480_30_vbr_500_99_40000000.mp4}"',)
'h264'
<type 'str'>
Traceback (most recent call last):
  File "streaming_verification/src/streaming_verification/scripts/streaming_verification.py", line 184, in run
    self.streaming.dump_file(export_fname, 5, codec_type)
  File "streaming_verification/src/streaming_verification/scripts/streaming.py", line 57, in dump_file
    cmd_str = " ".join(cmd)
TypeError: sequence item 3: expected string, tuple found

脚本源代码:

def dump_file(self,
              fname='',
              period=10,
              codec_type="h264"):

    if "h264" == codec_type:
        output_format = "--sout \"#standard{access=file,vcodec=h264,dst=%s.mp4}\"" % fname,
    elif "mjpeg" == codec_type:
        output_format =  "--sout \"#standard{access=file,vcodec=mjpg ,dst=%s.avi}\"" % fname,
    elif "mpeg" == codec_type :
        output_format =  "--sout \"#standard{access=file,vcodec=h264,dst=%s.mp4}\"" % …