python - 艰难地学习 Python，Ex 49 : Comparing objects using assert_equal

Question

是否可以使用 assert_equal 来比较对象？我一直看到这个错误:

AssertionError: <ex49.parser.Sentence object at 0x01F1BAF0> !=
<ex49.parser.Sentence object at 0x01F1BB10>

相关代码片段:

def test_parse_subject():

    testsentence = "princess go east"
    result = lexicon.scan(testsentence)
    Sent = parse_sentence(result)
    ResultSent = Sentence(('subject', 'princess'),
                      ('verb', 'go'),
                      ('object', 'east'))
    print ResultSent.subject
    print ResultSent.verb
    print ResultSent.object
    print Sent.subject
    print Sent.verb
    print Sent.object
    assert_equal(Sent, ResultSent)

屏幕上的打印输出表明对象具有相同的内容 - 但出现断言错误。为什么是这样？有什么方法可以使用 assert_equal 来覆盖它吗？

Answer 1

我相信您需要在 Sentence 类上实现 __eq__ 方法。

assertEqual(first, second, msg=None)¶ Test that first and second are equal. If the values do not compare equal, the test will fail.

In addition, if first and second are the exact same type and one of list, tuple, dict, set, frozenset or unicode or any type that a subclass registers with addTypeEqualityFunc() the type-specific equality function will be called in order to generate a more useful default error message (see also the list of type-specific methods).

Python unittest documentation

The correspondence between operator symbols and method names is as follows: xlt(y), x<=y calls x.le(y), x==y calls x.eq(y), x!=y and x<>y call x.ne(y), x>y calls x.gt(y), and x>=y calls x.ge(y).

Python data model documentation

一个例子:

import unittest


class A:

    def __init__(self, num):
        self.num = num

    def __eq__(self, other):
        return self.num == other.num


class Test(unittest.TestCase):

    def test(self):
        a1 = A(1)
        a12 = A(1)
        a2 = A(2)

        self.assertEqual(a1, a1, 'a1 != a1')
        self.assertEqual(a1, a12, 'a1 != a12')
        self.assertEqual(a1, a2, 'a1 != a2')

def main():
    unittest.TestRunner(Test())

if __name__ == '__main__':
    unittest.main()

现在评论 __eq__ 方法并查看差异。