Python Index Error List of index out of range答案

【问题标题】：Python Index Error List of index out of rangePython Index Error List of index out of range
【发布时间】：2013-04-27 11:36:21
【问题描述】：

我有一个 python 代码，它可以向设备发送串行命令并从中获得回复。

 def control(command):
     serialport= serial.Serial ("/dev/ttyAMA0", 9600, timeout=0.5)
     serialport.write(command)
     return serialport.readlines(1)

我有一本字典，它映射了一些要传递给command 的代码。然后我会把回复打印出来。

response = control(code_map.get(key,None))
print response, type(response)

编辑：打印输出的示例是['\x03O?0201\r'] <type 'list'>

收到回复后，我必须检查回复中的某些字符：

if "O?" in response[0]:
    if "01" in response[0]:
        if "0100" in response[0]:
            status="off"
        else:
            status="on"
    else:
        status="off"

如果只回复一次就可以了。但是当有 2 个或更多请求时，它会引发索引错误并且不会显示状态。

这是我的 javascript 发布并获得状态回复：

        $('#monitor').click(function(){
            setInterval(function(){
                    $('#status_table tr [id^="monitor_"]:checked').each(function () {
                        monitoring($(this).parents('tr'));
                     });
                },15000);
        });

        function monitoring($row) {
            $('#test').append("checked");
            fbType = $row.find('td:nth-child(3)').html();
            fbNum = $row.find('td:nth-child(4)').html();
            eachStatus =$row.find('td:nth-child(5)').attr('id');
            $('#test').append(fbType + ' '+ fbNum+' '+ eachStatus +'<br>');

            $.post('/request', {inputText: fbNum,key_pressed: fbType.toString()}).done(function (reply) {
                if (reply == "on") {
                    $('#status_table tr #status_'+eachStatus).append("on");
                    $('#test').append("on");
                } else if (reply =="off") {
                    $('#status_table tr #'+eachStatus).empty().append("off");
                    $('#test').append("off");
                }
            });
        }

追溯：

[03/May/2013:14:36:35] HTTP Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/CherryPy-3.2.2-py2.7.egg/cherrypy/_cprequest.py", line 656, in respond
    response.body = self.handler()
  File "/usr/local/lib/python2.7/dist-packages/CherryPy-3.2.2-py2.7.egg/cherrypy/lib/encoding.py", line 188, in __call__
    self.body = self.oldhandler(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/CherryPy-3.2.2-py2.7.egg/cherrypy/_cpdispatch.py", line 34, in __call__
    return self.callable(*self.args, **self.kwargs)
  File "remote_control_keypad_new52.py", line 677, in request
    if "O?" in response[0]:
IndexError: list index out of range

[03/May/2013:14:36:35] HTTP
Request Headers:
  Content-Length: 31
  REFERER: http://localhost:8080/
  HOST: localhost:8080
  ORIGIN: http://localhost:8080
  CONNECTION: Keep-Alive
  Remote-Addr: 127.0.0.1
  ACCEPT: */*
  USER-AGENT: Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en-us) AppleWebKit/535+ (KHTML, like Gecko) Version/5.0 Safari/535.22+ Midori/0.4
  X-REQUESTED-WITH: XMLHttpRequest
  ACCEPT-LANGUAGE: en-us;q=0.750
  Content-Type: application/x-www-form-urlencoded; charset=UTF-8
  ACCEPT-ENCODING: gzip, deflate
127.0.0.1 - - [03/May/2013:14:36:35] "POST /request HTTP/1.1" 500 1460 "http://localhost:8080/" "Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en-us) AppleWebKit/535+ (KHTML, like Gecko) Version/5.0 Safari/535.22+ Midori/0.4"
['\x03O?0101\r\x03O?0201\r'] <type 'list'>
on
127.0.0.1 - - [03/May/2013:14:36:36] "POST /request HTTP/1.1" 200 2 "http://localhost:8080/" "Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en-us) AppleWebKit/535+ (KHTML, like Gecko) Version/5.0 Safari/535.22+ Midori/0.4"
Button one is assigned with Response number None
Button one is assigned with Response number None
Button one is assigned with Response number None
output number selected is 01
R!None
R!None
R!None
R!None
Button one is assigned with Response number None
Button one is assigned with Response number None
Button one is assigned with Response number None
output number selected is 02
R!None
R!None
R!None
R!None
[03/May/2013:14:36:50] HTTP Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/CherryPy-3.2.2-py2.7.egg/cherrypy/_cprequest.py", line 656, in respond
    response.body = self.handler()
  File "/usr/local/lib/python2.7/dist-packages/CherryPy-3.2.2-py2.7.egg/cherrypy/lib/encoding.py", line 188, in __call__
    self.body = self.oldhandler(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/CherryPy-3.2.2-py2.7.egg/cherrypy/_cpdispatch.py", line 34, in __call__
    return self.callable(*self.args, **self.kwargs)
  File "remote_control_keypad_new52.py", line 674, in request
    response = comfort_control(code_map.get(key,None))
  File "remote_control_keypad_new52.py", line 639, in comfort_control
    return serialport.readlines(1)
  File "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 456, in read
    raise SerialException('device reports readiness to read but returned no data (device disconnected?)')
SerialException: device reports readiness to read but returned no data (device disconnected?)

[03/May/2013:14:36:50] HTTP
Request Headers:
  Content-Length: 31
  REFERER: http://localhost:8080/
  HOST: localhost:8080
  ORIGIN: http://localhost:8080
  CONNECTION: Keep-Alive
  Remote-Addr: 127.0.0.1
  ACCEPT: */*
  USER-AGENT: Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en-us) AppleWebKit/535+ (KHTML, like Gecko) Version/5.0 Safari/535.22+ Midori/0.4
  X-REQUESTED-WITH: XMLHttpRequest
  ACCEPT-LANGUAGE: en-us;q=0.750
  Content-Type: application/x-www-form-urlencoded; charset=UTF-8
  ACCEPT-ENCODING: gzip, deflate
127.0.0.1 - - [03/May/2013:14:36:50] "POST /request HTTP/1.1" 500 1839 "http://localhost:8080/" "Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en-us) AppleWebKit/535+ (KHTML, like Gecko) Version/5.0 Safari/535.22+ Midori/0.4"
['\x03O?0101\r\x03O?0201\r'] <type 'list'>
on
127.0.0.1 - - [03/May/2013:14:36:51] "POST /request HTTP/1.1" 200 2 "http://localhost:8080/" "Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en-us) AppleWebKit/535+ (KHTML, like Gecko) Version/5.0 Safari/535.22+ Midori/0.4"
^C[03/May/2013:14:36:56] ENGINE Keyboard Interrupt: shutting down bus
[03/May/2013:14:36:56] ENGINE Bus STOPPING

【问题讨论】：

在中断的情况下，print response 打印什么？
类似 ['\x03O?0101\r']
如果是这种情况，response[0] 无法引发 IndexError。你能显示你的完整回溯
对不起，什么是回溯？是cmd窗口上的吗？是的，它只回复一次就可以了……
好的，添加回溯:)

标签： javascript python list indexing

【解决方案1】：

也许您的回复是一个空列表

>>> response = []
>>> response[0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list index out of range

也许您的设备并不总是足够快，无法对此做出响应

serialport.write(command)
return serialport.readlines(1)

特别是如果您有 2 个重叠的请求，您需要确保您的程序一次将它们提供给设备。

【讨论】：

opps 是control。它打印出类似 ['\x03O?0101\x']
我使用树莓派作为网络服务器。我将发送多个请求。我应该怎么做才能确保请求被一一发送？