Assert isinstance python что это

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Вы можете видеть, что выводится только один вывод, а последний не выполняется, потому что assert (3 == 4) вызывает исключение.

2. isinstance
Описание функции:

Когда мы определяем класс, мы фактически определяем тип данных. Типы данных, которые мы определяем, не отличаются от типов данных, которые поставляются с Python, таких как str, list и dict:

Чтобы определить, относится ли переменная к определенному типу, вы можете использовать isinstance () для определения:

Python assertIsInstance()

Summary: in this tutorial, you’ll learn how to use Python assertIsInstance() method to test if an object is an instance of a class.

Introduction to the Python assertIsInstance() method

The assertIsInstance() is a method of the TestCase class of the unittest module. The assertIsInstance() method tests if an object is an instance of a class.

The following shows the syntax of the assertIsInstance() method:

obj is the object to test.
cls is a class or a tuple of classes.
msg is an optional string that will be displayed if the obj is not an instance of the cls class.

Internally, the assertIsInstance() uses the isinstance() function to check if the object is an instance of the cls class.

If the cls is not the class of the obj but the base class of the class of the obj, the test will also pass.

Since the object class is the base class of all classes, the assertIsInstance(obj, object) will always pass.

Python assertIsInstance() method examples

Let’s create a shape.py module with two classes Shape and Square . The Shape class is the base class of the Square class:

To make it simple, the Shape and Square classes have no implementation.

1) Using the Python assertIsInstance() method example

The following example uses the assertIsInstance() method to test if the square object is an instance of the Square class:

Because the square instance variable is an object of the Square class, the test passes.

2) Using the Python assertIsInstance() method with a base class example

The following example uses the assertIsInstance() method to test if the square is an instance of the Shape class:

3) Using the Python assertIsInstance() method to test if an object is an instance of the object class

The following example uses assertIsInstance() method to test if the square instance variable is an instance of the object class:

Python assertIsNotInstance() method

The assertIsNotInstance() is the opposite of the assertIsInstance() method. It tests if an object is not an instance of a class:

In this example, the test_is_not_instance() method uses the assertIsNotInstance() method to test if a Shape object is an instance of the Square class.

Why Learn Assert Statements For Unit Tests?

Cover Image for The Complete List Of Python Assert Statements

Knowing how to write assert statements in Python allows you to easily write mini-tests for your code.

Additionally testing frameworks such as PyTest can work directly with assert statements to form fully functioning UnitTests.

You can also find a list of all of the different standard UnitTest Module examples here.

Firstly let’s review all of the different types of assert statements that we can make for PyTest.

PyTest Python Assert Statements List

NB: Whenever you see # Success Example, this means that the assert test will succeed. However when you see # Fail Example, this means that the assert test will fail.

1. Equal to or not equal to [value]

2. type() is [value]

3. isinstance

4. Boolean is [Boolean Type]

5. in and not in [iterable]

6. Greater than or less than [value]

7. Modulus % is equal to [value]

8. any() assert statements

Notice that the example list python list is True because at least one of the numbers is not a 0, all numbers above 0 are ‘Truthy’.

9. all() assert statements

10. Custom Python Objects

It’s possible to identify if a class is a specific type of object. We can do this by using:

11. Iterables

It’s also possible to determine whether a variable is an iterable with:

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Combining Multiple And / Or Statements With Assert Statements:

It’s also possible to combine multiple conditions with either OR or AND and to test the chained commands with the assert statement:

Testing Multiple Commands

Also we can test more than one thing at a time by having multiple assert statements inside of the same Python method:

Python 3.x UnitTest Assert Methods

Below you’ll find a list of all of the UnitTest Assert Methods:

Method	Checks	Version
assertEqual	a == b	3.x
assertNotEqual	a != b	3.x
assertTrue	bool(x) is True	3.x
assertFalse	bool(x) is False	3.x
assertIs	a is b	3.x
assertIsNot	a is not b	3.x
assertIsNone	x is None	3.x
assertIsNotNone	x is not None	3.x
assertIn	a in b	3.x
assertNotIn	a not in b	3.x
assertIsInstance	is instance(a,b)	3.x
assertNotIsInstance	not is instance(a,b)	3.x
assertRaises	fun(args,*kwds) raises exc	3.x
assertRaisesRegexp	fun(args,*kwds) raises exc(regex)	3.x
assertAlmostEqual	round(a-b,7) == 0	3.x
assertNotAlmostEqual	round(a-b,7) != 0	3.x
assertGreater	a > b	3.x
assertGreaterEqual	a >= b	3.x
assertLess	a < b	3.x
assertLessEqual	a <= b	3.x
assertRegexpMatches	r.search(s)	3.x
assertNotRegexpMatches	not r.search(s)	3.x
assertItemsEqual	sorted(a) == sorted(b)	3.x
assertDictContainsSubset	all the key/value pairs in a exist in b	3.x
assertMultiLineEqual	strings	3.x
assertSequenceEqual	sequences	3.x
assertListEqual	lists	3.x
assertTupleEqual	tuples	3.x
assertSetEqual	sets or frozensets	3.x
assertDictEqual	dicts	3.x

Typing Assert Statements

As well as using simple assert statements, by importing the types module of python we can make more abstract assert statements on specific Types:

Above we’ve tested two class instance methods to see if either of them is a lambda: x style function!

You can find all of the different types here.

Hopefully this provides you with an extensive list of assert statements and methods for your Unit Tests.

Please let me know if you have any more examples that you’d like me to add them to this post ��