python 错误--UnboundLocalError: local variable '**' referenced before assignment

 val = 9
 def test(flag):
     if flag:
         val = 1
     else:
         print("test")
     return val 

 if __name__ == '__main__':
     ret = test(0)
     print(ret)

运行如下：

linux@linux-desktop:~$ python3.3 test.py
fuck
Traceback (most recent call last):
File "test.py", line 10, in <module>
ret = test(0)
File "test.py", line 7, in test
return val
UnboundLocalError: local variable 'val' referenced before assignment

解释如下：

1.意思：

本地变量xxx引用前没定义。

2.错误原因：

   
在于python没有变量的声明 , 所以它通过一个简单的规则找出变量的范围 ：如果有一个函数内部的变量赋值
，该变量被认为是本地的，所以如果有修改变量的值就会变成局部变量。

3.解决方法：用global关键字来进行说明该变量是全局变量
python代码：
val=9
def test(flag):
    global
val
    if
flag: 
       
val = 1 
   
else: 
       
print(test) 
    return
val

本地变量xxx引用前没定义。

项目中遇到错误如下：

root@UA4300D-spa:~/hanhuakai/pro_07/0703/webview# python3 app.py
ERROR:tornado.application:Uncaught exception GET /top (192.168.2.144)
HTTPRequest(protocol='http', host='192.168.5.41:7777', method='GET', uri='/top', version='HTTP/1.1', remote_ip='192.168.2.144', headers={'Accept-Language': 'zh-cn,zh;q=0.8,en-us;q=0.5,en;q=0.3', 'Accept-Encoding': 'gzip, deflate', 'Host': '192.168.5.41:7777', 'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8', 'User-Agent': 'Mozilla/5.0 (Windows NT 5.1; rv:30.0) Gecko/20100101 Firefox/30.0', 'Connection': 'keep-alive', 'Referer': 'http://192.168.5.41:7777/', 'Cache-Control': 'max-age=0', 'If-None-Match': '"56b2971f04441fe9644324362487e88a84a776de"'})
Traceback (most recent call last):
File "/usr/lib/python3.2/site-packages/tornado/web.py", line 1218, in _when_complete
callback()
File "/usr/lib/python3.2/site-packages/tornado/web.py", line 1239, in _execute_method
self._when_complete(method(*self.path_args, **self.path_kwargs),
File "app.py", line 21, in get
self.render("top.htm")
File "/usr/lib/python3.2/site-packages/tornado/web.py", line 615, in render
html = self.render_string(template_name, **kwargs)
File "/usr/lib/python3.2/site-packages/tornado/web.py", line 722, in render_string
return t.generate(**namespace)
File "/usr/lib/python3.2/site-packages/tornado/template.py", line 278, in generate
return execute()
File "top_htm.generated.py", line 5, in _tt_execute
_tt_tmp = _tt_modules.Workstate() # top.htm:34
File "/usr/lib/python3.2/site-packages/tornado/web.py", line 1313, in render
rendered = self._active_modules[name].render(*args, **kwargs)
File "app.py", line 2043, in render
info = s.faultyinfo()
File "/usr/lib/python3.2/xmlrpc/client.py", line 1076, in __call__
return self.__send(self.__name, args)
File "/usr/lib/python3.2/xmlrpc/client.py", line 1403, in __request
verbose=self.__verbose
File "/usr/lib/python3.2/xmlrpc/client.py", line 1117, in request
return self.single_request(host, handler, request_body, verbose)
File "/usr/lib/python3.2/xmlrpc/client.py", line 1132, in single_request
return self.parse_response(resp)
File "/usr/lib/python3.2/xmlrpc/client.py", line 1303, in parse_response
return u.close()
File "/usr/lib/python3.2/xmlrpc/client.py", line 648, in close
raise Fault(**self._stack[0])
xmlrpc.client.Fault: <Fault 1: "<class 'UnboundLocalError'>:local variable 'str_problem_in' referenced before assignment FILENAME: /usr/lib/python3.2/site-packages/ssapi/fm/faultyinfo.py LINE: 912 NAME: print_status_record">
ERROR:tornado.access:500 GET /top (192.168.2.144) 413.94ms

部分代码如下：

 def print_status_record(srp, faulty_item):
     global fmadm_msghdl
     uurp = srp.uurec
     str_time = time.ctime(uurp[0].sec)
     faulty_item.time = str_time            #"TIME"
     faulty_item.event_id = uurp[0].uuid    #"EVENT-ID"
     faulty_item.msg_id = srp.msgid         #"MSG-ID"
     faulty_item.severity = srp.severity    #"SEVERITY"

     faulty_item.host = srp.host.server          #"Host"
     if srp.host.domain :
         faulty_item.domain = srp.host.domain    #"Domain"
     else:
         faulty_item.domain = "None"

     faulty_item.platform = srp.host.platform    #"Platform"
     str_class_id = srp.host.chassis if srp.host.chassis else "None"
     str_product_sn = srp.host.product_sn if srp.host.product_sn else "None"

     faulty_item.class_id = str_class_id         #"Chassis_id"
     faulty_item.product_sn = str_product_sn     #"Product_sn"

     if srp.classt :                             #"Fault class"
         str_faulty_class = get_name_list(srp.classt, \
                 "Fault class :", srp.classt[0].pct, None)
         faulty_item.faulty_class = str_faulty_class
     else:
         faulty_item.faulty_class = "None"

     if srp.asru :                               #"Affects"
         status = asru_same_status(srp.asru)
         if status != -1 :
             msg_name_list = get_name_list(srp.asru,"Affects     :", 0, None)
             msg_asru_status = print_asru_status(status, "             ")
             str_affects = msg_name_list + msg_asru_status
         else:
             str_affects = get_name_list(srp.asru,"Affects     :", 0, \
                     print_asru_status)
         faulty_item.affects = str_affects
     else:
         faulty_item.affects = "None"

     if not srp.fru or not srp.asru :            #"Problem in"
         if srp.resource :
             status = asru_same_status(srp.resource)
             if status != -1 :
                 msg_name_list = get_name_list(srp.resource, \
                         "Problem in  :", 0, None)
                 msg_rsrc_status = print_rsrc_status(status, "             ")
                 str_problem_in = msg_name_list + msg_rsrc_status
             else:
                 str_problem_in = get_name_list(srp.resource, \
                         "Problem in  :", 0, print_rsrc_status)
         faulty_item.problem_in = str_problem_in
     else:
         faulty_item.problem_in = "None"

     if srp.fru :                                #"FRU"
         status = asru_same_status(srp.fru)
         if status != -1 :
             msg_name_list = get_name_list(srp.fru, "FRU         :", \
                     100 if srp.fru[0].pct == 100 else \
                     srp.fru[0].max_pct, None)
             msg_fru_status = print_fru_status(status, "             ")
             str_fru = msg_name_list + msg_fru_status
         else:
             str_fru = get_name_list(srp.fru, "FRU         :", 100 \
                     if srp.fru[0].pct == 100 else srp.fru[0].max_pct, \
                     print_fru_status)
         faulty_item.fru = str_fru
     else:
         faulty_item.fru = "None"

     if srp.serial and not serial_in_fru(srp.fru, srp.serial) and \
             not serial_in_fru(srp.asru, srp.serial) :
         str_serial_id = get_name_list(srp.serial, "Serial ID.  :", 0, None)
         faulty_item.serial_id = str_serial_id
     else:
         faulty_item.serial_id = "None"          #"Serial ID"

     nvl = srp.uurec[0].event
     _fmd_msg_getitem_nv = libfmd_msg.fmd_msg_getitem_nv
     _fmd_msg_getitem_nv.restype = c_char_p

     description = _fmd_msg_getitem_nv(fmadm_msghdl, None, nvl, \
             FMD_MSG_ITEM_DESC)
     faulty_item.description = description.decode('UTF-8')   #"Description"

     response = _fmd_msg_getitem_nv(fmadm_msghdl, None, nvl, \
             FMD_MSG_ITEM_RESPONSE)
     faulty_item.response = response.decode('UTF-8')         #"Response"

     impact = _fmd_msg_getitem_nv(fmadm_msghdl, None, nvl, \
             FMD_MSG_ITEM_IMPACT)
     faulty_item.impact = impact.decode('UTF-8')             #"Impact"

     action = _fmd_msg_getitem_nv(fmadm_msghdl, None, nvl, \
             FMD_MSG_ITEM_ACTION)
     faulty_item.action = action.decode('UTF-8')             #"Action"

     return faulty_item

解析：

当if not srp.fru or not srp.asru成立，并且if srp.resource不成立时，这是便直接执行：faulty_item.problem_in = str_problem_in
因此就会出现以上错误信息，值得注意！
错误修改如下：

     if not srp.fru or not srp.asru :            #"Problem in"
         if srp.resource :
             status = asru_same_status(srp.resource)
             if status != -1 :
                 msg_name_list = get_name_list(srp.resource, \
                         "Problem in  :", 0, None)
                 msg_rsrc_status = print_rsrc_status(status, "             ")
                 str_problem_in = msg_name_list + msg_rsrc_status
             else:
                 str_problem_in = get_name_list(srp.resource, \
                         "Problem in  :", 0, print_rsrc_status)
12             faulty_item.problem_in = str_problem_in
13         else:
14             faulty_item.problem_in = "None"
     else:
         faulty_item.problem_in = "None"