导入时间的另一个UnboundLocalError问题

Question

我正在使用多线程+类：

import time
class CounterThread(threading.Thread):    
   def __init__(self,queue, obj)
       self.obj = obj

   def run(self):
      while True:
         result = self.process()
         self.out_queue.put(result)
         time.sleep(self.obj['wait_Time'])

   def process(self):
      results = ''
      subprocess.check_output(<command> , shell=True) #command for starting sample
      time.sleep(self.obj['sample_Time'])
      status_results = subprocess.check_output(<command>, shell=True) #reads sample output
      lines = status_results.splitlines()
      for lines in lines :
         words = line.split()
         if words[0] == 'Node' :
            results += ('Node=' + words[1] + '\n')
         else if words[0] == 'End-Time' :
            results += 0'End-Time=' + words[1] + ' ' + words[2] + '\n')
      subprocess.check_output(<command>, shell=True) #deletes sample 
      return results

行time.sleep(self.obj['sample_Time'])是我收到unboundLocalError的地方。我很确定这是一个范围问题，但不知道如何解决它。如果我删除该行，代码运行正常。

以下是追溯：

Traceback (most recent call last):
  File "/usr/software/lib/python2.7/threading.py", line 808 in __bootstrap_inner
    self.run()
  File "counter_extraction.py", line 29, in run
    result = self.process()
  File "counter_extract.py", line 42, in process
    time.sleep(self.obj['sample_Time'])
UnboundLocalError: local variable 'time' referenced before assignment