为什么 __name__ 等于 __main__？

Question

I understand that __main__ is the name of __main__.py , which in this case is test_employee . But what I don't understand is the unittest module and the class that I want to test are being imported. Then why __name__ is still same as __main__ ? As I understood, __name__ represents the modules being imported.

test_employee.py

import unittest

from employee import Employee

class TestEmployee(unittest.TestCase):

    def setUp(self):
        self.employee1 = Employee('June', 'July')
        self.employee2 = Employee('Jane', 'Marshal')
    
    def test_give_default_raise(self):
        self.assertEqual(5000, self.employee1.annual_salary)

    def test_give_custom_raise(self):
        self.employee2.give_raise(1000)
        self.assertEqual(6000, self.employee2.annual_salary)

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

Answer 1

__main__ is a very particular function of python. It has mainly two interests:

• if __name__ == '__main__' condition
• __main__.py file for a module (which is not the purpose hier)

When importing a module, the __name__ attribute of this module is set to the name of the module (ie the file name without the.py extension).

>>> import my_module
>>> my_module.__name__
'my_module'

>>> import my_module.submodule
>>> my_module.submodule.__name__
'my_module.submodule'

However, if the attribute is called from the main runtime environment (which is the main use case), then the variable will always contain the value '__main__' . The main purpose of this is to test whether the main script is called from the main runtime environment or not. This is usefull to differentiate the case where the module is called directly (for instance from command line) and the one where it is loaded from another module (to launch an argparse, for example...)

Nevertheless, it is recommended to put as little code as possible under the condition if __name__ == '__main__' to avoid errors.

It is recommended to do as follows:

# echo.py

import shlex
import sys

def echo(phrase: str) -> None:
   """A dummy wrapper around print."""
   # for demonstration purposes, you can imagine that there is some
   # valuable and reusable logic inside this function
   print(phrase)

def main() -> int:
    """Echo the input arguments to standard output"""
    phrase = shlex.join(sys.argv)
    echo(phrase)
    return 0

if __name__ == '__main__':
    sys.exit(main())

Answer 2

Functions and classes that are defined, but none of their code runs. When You Use name == main its Executed when invoked directly as when its invoked directly name will be main.

Answer 3

You are running the test inside main module..not the Employee(which is being imported)..so when you setUp the unittest, the instance of Employee becomes the instant of TestEmployee class..Hope it was clear to you!!!

Answer 4

When you run your script, the __name__ variable equals __main__ . When you import a script, __name__ will contain the name of the script.

So when you run test_employee.py :

• __name__ in test_employee.py will be __main__
• __name__ in employee.py will be employee
• __name__ in unittest.py will be unittest

For more information you can have a look here: https://www.freecodecamp.org/news/whats-in-a-python-s-name-506262fe61e8/

Answer 5

The __name__ and __main__ has been very well described in below Python documentation:

https://docs.python.org/3/library/__main__.html#:~:text=%C2%B6,entry%20point%20to%20the%20application .