mock method from standard package

mock_os_path_exists.py

from os.path import exists as orig_exists
from unittest.mock import Mock

exists = orig_exists

def new_exists(file):
    print(f"new_exists: checking if '{file}' exists:", orig_exists(file))
    print("but will send exists = True")
    return True


def patch_exists():
    global exists
    exists = Mock()
    exists.side_effect = new_exists


def test_file_exists(file):
    rv = exists(file)
    assert rv == True


def test_file_not_exists(file):
    rv = exists(file)
    assert rv == False


if __name__ == "__main__":
    file = "d:/non_existing_file.txt"
    test_file_not_exists(file)
    patch_exists()
    test_file_exists(file)
    print("Success!")