Python模擬返回初始預定義值返回默認值

我在模擬消息隊列，我希望它返回2條消息，然後在每次調用時都返回None（模擬消息隊列現在爲空）。但是，在第三個消息調用之後，我從模擬框架中得到一個錯誤，說沒有「下一個」值。Python模擬返回初始預定義值返回默認值

下面是一個例子：

from mock import MagicMock 

mock_message_queue = MagicMock(name='message_queue') 
expected_messages = ['message 1', 'message 2', None] 
mock_message_queue.fetch.side_effect = expected_messages 

print('mock_message_queue.fetch() = {}'.format(mock_message_queue.fetch())) 
print('mock_message_queue.fetch() = {}'.format(mock_message_queue.fetch())) 
print('mock_message_queue.fetch() = {}'.format(mock_message_queue.fetch())) 
print('mock_message_queue.fetch() = {}'.format(mock_message_queue.fetch()))

輸出：

mock_message_queue.fetch() = message 1 
mock_message_queue.fetch() = message 2 
mock_message_queue.fetch() = None 
Traceback (most recent call last): 
    File "/home/wsi/.PyCharm2017.1/config/scratches/mock_message_bus.py", line 10, in <module> 
    print('mock_message_queue.fetch() = {}'.format(mock_message_queue.fetch())) 
    File "/usr/local/lib/python3.5/dist-packages/mock/mock.py", line 1062, in __call__ 
    return _mock_self._mock_call(*args, **kwargs) 
    File "/usr/local/lib/python3.5/dist-packages/mock/mock.py", line 1121, in _mock_call 
    result = next(effect) 
StopIteration 

Process finished with exit code 1

所以基本上我想它總是返回無返回 '消息2' 之後。有人知道怎麼做嗎？

來源

2017-06-21 Craig

問題是你需要值列表的最後一個元素無限重複。您可以使用itertools.repeat進行此操作，並使用itertools.chain將其加入實際值列表中。

expected_messages = itertools.chain(['message 1', 'message 2'], itertools.repeat(None))

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2017-06-21 12:49:11

Python模擬返回初始預定義值返回默認值

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