Python模拟返回初始预定义值返回默认值

我在模拟消息队列，我希望它返回2条消息，然后在每次调用时都返回None（模拟消息队列现在为空）。但是，在第三个消息调用之后，我从模拟框架中得到一个错误，说没有“下一个”值。Python模拟返回初始预定义值返回默认值

下面是一个例子：

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()))

输出：

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

所以基本上我想它总是返回无返回 '消息2' 之后。有人知道怎么做吗？

来源

2017-06-21 Craig

问题是你需要值列表的最后一个元素无限重复。您可以使用itertools.repeat进行此操作，并使用itertools.chain将其加入实际值列表中。

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

来源

2017-06-21 12:49:11

Python模拟返回初始预定义值返回默认值

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