python--分支和assert断言（七）

python--分支和assert断言（七）

                    #分支和assert
score = int(input('请输入一个分数'))
if score == 100:
    print('成绩为A')
elif 99>=score>=90:
    print('成绩为B')
elif 89>=score>=80:
    print('成绩为C')
elif 79>=score>=60:
    print('成绩为D')
elif score<59:
    print('成绩为不及格')
else:
    print('输入的成绩不正确')

# assert（断言）当这个关键字后边的条件为假的时候，程序自动崩溃并抛出AssertionError的异常
assert 3<4

这里介绍几个常用断言的使用方法，可以一定程度上帮助大家对预期结果进行判断。-

assertEqual

assertNotEqual

assertTrue

assertFalse

assertIsNone

assertIsNotNone

assertEqual 和 assertNotEqual

assertEqual：如两个值相等，则pass

assertNotEqual：如两个值不相等，则pass

使用方法:
assertEqual(first,second,msg)其中first与second进行比较，如果相等则通过；msg为失败时打印的信息，选填；断言assertNotEqual反着用就可以了。

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assertTrue和assertFalse

assertTrue：判断bool值为True，则pass

assertFalse：判断bool值为False，则Pass

使用方法:
assertTrue(expr,msg)其中express输入相应表达式，如果表达式为真，则pass；msg选填；断言assertFalse如果表达式为假，则pass

assertIsNone和assertIsNotNone

assertIsNone：不存在，则pass

assertIsNotNone：存在，则pass

使用方法：
assertIsNone(obj,msg)检查某个元素是否存在

assertEqual(a, b)     a == b      
assertNotEqual(a, b)     a != b      
assertTrue(x)     bool(x) is True      
assertFalse(x)     bool(x) is False      
assertIs(a, b)     a is b     2.7
assertIsNot(a, b)     a is not b     2.7
assertIsNone(x)     x is None     2.7
assertIsNotNone(x)     x is not None     2.7
assertIn(a, b)     a in b     2.7
assertNotIn(a, b)     a not in b     2.7
assertIsInstance(a, b)     isinstance(a, b)     2.7
assertNotIsInstance(a, b)     not isinstance(a, b)     2.7

assertAlmostEqual(a, b)     round(a-b, 7) == 0      
assertNotAlmostEqual(a, b)     round(a-b, 7) != 0      
assertGreater(a, b)     a > b     2.7
assertGreaterEqual(a, b)     a >= b     2.7
assertLess(a, b)     a < b     2.7
assertLessEqual(a, b)     a <= b     2.7
assertRegexpMatches(s, re)     regex.search(s)     2.7
assertNotRegexpMatches(s, re)     not regex.search(s)     2.7
assertItemsEqual(a, b)     sorted(a) == sorted(b) and works with unhashable objs     2.7
assertDictContainsSubset(a, b)     all the key/value pairs in a exist in b     2.7
assertMultiLineEqual(a, b)     strings     2.7
assertSequenceEqual(a, b)     sequences     2.7
assertListEqual(a, b)     lists     2.7
assertTupleEqual(a, b)     tuples     2.7
assertSetEqual(a, b)     sets or frozensets     2.7
assertDictEqual(a, b)     dicts     2.7
assertMultiLineEqual(a, b)     strings     2.7
assertSequenceEqual(a, b)     sequences     2.7
assertListEqual(a, b)     lists     2.7
assertTupleEqual(a, b)     tuples     2.7
assertSetEqual(a, b)     sets or frozensets     2.7assertDictEqual(a, b)     dicts     2.7