python - 断言一个操作引发了一个 Stopiteration

Question

我有一个生成器，我想确认它已经结束(在程序的某个点。我在 python 2.7 中使用 unittest

# it is a generator whould have only one item
item = it.next()
# any further next() calls should raise StopIteration
self.assertRaises(StopIteration, it.next())

但它失败并显示消息

======================================================================
ERROR: test_productspider_parse_method (__main__.TestMyMethods)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/myName/tests/__main__.py", line 94, in test_my_method
    self.assertRaises(StopIteration, it.next())
StopIteration

----------------------------------------------------------------------

Answer 1

您需要传递方法本身而不是调用方法。换句话说，去掉括号。

self.assertRaises(StopIteration, it.next)

或者您可以将其用作上下文管理器:

with self.assertRaises(StopIteration):
    it.next()