Different behavior with mock to same class or different class

Bug report

Bug description:

import unittest
from unittest.mock import patch

class Number:
    def __init__(self, value):
        print(f'init: {value}')
        self.value = value

    def get_value(self):
        return self.value

class MockNumber:
    def __init__(self, value):
        print(f'mock init: {value}')
        self.value = value

    def get_value(self):
        return self.value

class TestNumber(unittest.TestCase):
    def setUp(self):
        pass

    def tearDown(self):
        pass

    def test_number(self):
        number = Number(1)
        with patch.object(Number, '__new__', return_value=number):
            test = Number(2)
            print(test.get_value())

        mock_number = MockNumber(1)
        with patch.object(Number, '__new__', return_value=mock_number):
            test = Number(2)
            print(test.get_value())

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

The output is

init: 1
init: 2
2
mock init: 1
1
.
----------------------------------------------------------------------
Ran 1 test in 0.001s

OK

When mock the function new of class Number to return an instance of MockNumber, the behavior is simple: just return the instance of MockNumber.
But when mock the function to return an instance of Number, the function of init will still be called.

CPython versions tested on:

3.11

Operating systems tested on:

Linux

从提供的unittest开始，比较patch.object(Number, 'new')返回Number与返回MockNumber时的情况。跟踪Python在__new__和__init__相关的对象构造行为，然后确定这种差异是否是有意的；完成条件是确认该行为，并提供适当的回归覆盖或文档。