ModuleNotFoundError¶

ModuleNotFoundError is raised when Python cannot find a module that is given in an import statement. A Python module is a file that ends in .py. Any folder that contains an __init__.py is also a Python module

requirements¶

I open a terminal to run makePythonTdd.sh with module_not_found_error as the name of the project
```
./makePythonTdd.sh module_not_found_error
```
on Windows without Windows Subsystem for Linux use makePythonTdd.ps1 instead of makePythonTdd.sh
```
./makePythonTdd.ps1 module_not_found_error
```
it makes the folders and files that are needed, installs packages, runs the first test, and the terminal shows AssertionError
```
E       AssertionError: True is not false

tests/test_module_not_found_error.py:7: AssertionError
```
I hold ctrl (Windows/Linux) or option or command (MacOS) on the keyboard and use the mouse to click on tests/test_module_not_found_error.py:7 to open it in the editor,
then I change True to False to make the test pass
```
7        self.assertFalse(False)
```
I change the name of the class to match the CapWords format to follow Python convention
```
4class TestModuleNotFoundError(unittest.TestCase):
```

test_module_not_found_error¶

RED: make it fail¶

I change test_failure to test_module_not_found_error

import unittest

class TestModuleNotFoundError(unittest.TestCase):

    def test_module_not_found_error(self):
        import src.module_00

the terminal shows ModuleNotFoundError

ModuleNotFoundError: No module called 'src.module_00'

because Python cannot find module_00.py in the src folder

I add the error to the list of Exceptions encountered in test_module_not_found_error.py
```
10# Exceptions Encountered
11# AssertionError
12# ModuleNotFoundError
```

GREEN: make it pass¶

I change module_not_found_error.py in the src folder to module_00.py and the test passes

REFACTOR: make it better¶

I add another import statement to test_module_not_found_error.py

    def test_module_not_found_error(self):
        import src.module_00
        import src.module_01

the terminal shows ModuleNotFoundError

ModuleNotFoundError: No module named 'src.module_01'

I make a new file named module_01.py in the src folder and the test passes

I close the file

I continue with another import statement in test_module_not_found_error.py

    def test_module_not_found_error(self):
        import src.module_00
        import src.module_01
        import src.module_02

the terminal shows ModuleNotFoundError

ModuleNotFoundError: No module called 'src.module_02'

I add module_02.py to the src folder and the terminal shows green again

I close the file

I add one last failing import statement for practice in test_module_not_found_error.py

    def test_module_not_found_error(self):
        import src.module_00
        import src.module_01
        import src.module_02
        import src.module_03

the terminal shows

ModuleNotFoundError: No module called 'src.module_03'

I add the file to the src folder and the test passes
I close the file

review¶

I ran a test for ModuleNotFoundError to practice making Python modules. Would you like to test AttributeError?

Click Here for the code I wrote in this chapter