IndexError：打印len（list）> 0之后，列表索引超出范围

Question

I literally have these two lines of code in sequence:

print(len(counter.ondas))
onda = counter.ondas[-1]

I got 13 printed for the first line and it crashed giving me tracebook to the onda = counter.ondas[-1] line saying IndexError: list index out of range right after printing len(list) .

It works thousands of times before crashing. I have no clue on how to approach this problem.

Output for print(counter.ondas) :

[Onda([<workers.mov.Mov object at 0x244EA050>], [Candle(4, 'GBP_JPY', Timestamp('2017-06-12 16:59:00'), 138.884, 138.897, 138.674, 138.76, 10957.0, True)]), Onda([<workers.mov.Mov object at 0x245073D0>], [Candle(4, 'GBP_JPY', Timestamp('2017-06-12 16:59:00'), 138.884, 138.897, 138.674, 138.76, 10957.0, True)...]

Output for print(type(counter.ondas)) :

<class 'list'>

Output for print(isinstance(counter.ondas, list)) :

True

Full Error Traceback

    Traceback (most recent call last):
      File "C:\Users\joaoa\AppData\Local\Programs\Python\Python36-32\lib\multiprocessing\pool.py", line 119, in worker
        result = (True, func(*args, **kwds))
      File "C:\Users\joaoa\AppData\Local\Programs\Python\Python36-32\lib\multiprocessing\pool.py", line 44, in mapstar
        return list(map(*args))
      File "C:\Users\joaoa\PycharmProjects\aquitania\general_manager.py", line 88, in load_observer_manager
        observer_manager.update_load_run_data()
      File "C:\Users\joaoa\PycharmProjects\aquitania\observer\management\observer_manager.py", line 78, in update_load_run_data
        self.load_run_data()
      File "C:\Users\joaoa\PycharmProjects\aquitania\observer\management\observer_manager.py", line 91, in load_run_data
        self.feeder.exec_df(df[self.start_date:])
      File "C:\Users\joaoa\PycharmProjects\aquitania\data_source\feeder.py", line 429, in exec_df
        self.feed(candle)
      File "C:\Users\joaoa\PycharmProjects\aquitania\data_source\feeder.py", line 98, in feed
        self.make_candle(ts, candle, criteria_table)
      File "C:\Users\joaoa\PycharmProjects\aquitania\data_source\feeder.py", line 126, in make_candle
        self.set_values(ts, candle)
      File "C:\Users\joaoa\PycharmProjects\aquitania\data_source\feeder.py", line 310, in set_values
        ts_obs.feed_complete(self._candles[ts])
      File "C:\Users\joaoa\PycharmProjects\aquitania\observer\management\observer_loader.py", line 100, in feed_complete
        observer.update_last_candle(candle, store_candle)
      File "C:\Users\joaoa\PycharmProjects\aquitania\observer\abstract\observer_abc.py", line 93, in update_last_candle
        self.set_observe(self.update_method(candle))
      File "C:\Users\joaoa\PycharmProjects\aquitania\observer\ondas\ondas_inside.py", line 393, in update_method
        self.update_routine(counter_id=2, candle=candle)
      File "C:\Users\joaoa\PycharmProjects\aquitania\observer\ondas\ondas_inside.py", line 412, in update_routine
        onda = list(counter.ondas)[-1]
    IndexError: list index out of range
    """

    The above exception was the direct cause of the following exception:

    Traceback (most recent call last):
      File "C:/Users/joaoa/PycharmProjects/aquitania/general_manager.py", line 145, in <module>
        gm.run()
      File "C:/Users/joaoa/PycharmProjects/aquitania/general_manager.py", line 113, in run
        list_of_observer_managers = self.load_all_observer_managers()
      File "C:/Users/joaoa/PycharmProjects/aquitania/general_manager.py", line 60, in load_all_observer_managers
        observer = currency_pool.map(self.load_observer_manager, list_of_currencies)
      File "C:\Users\joaoa\AppData\Local\Programs\Python\Python36-32\lib\multiprocessing\pool.py", line 266, in map
        return self._map_async(func, iterable, mapstar, chunksize).get()
      File "C:\Users\joaoa\AppData\Local\Programs\Python\Python36-32\lib\multiprocessing\pool.py", line 644, in get
        raise self._value
    IndexError: list index out of range

Answer 1

I was able to idenfity the issue. The error was being thrown in a separate process than the one that was being printed and for some reason the error ocurred only after the process that was printing the results was interrupted by another unrelated error.

Weird behavior, but now I am able to tackle the problem.

Debugging in a single process mode helped a lot.

Thank you for your help.