ModuleNotFoundError

what causes 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

preview

Here are the tests I have by the end of the chapter

import unittest


class TestModuleNotFoundError(unittest.TestCase):

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


# Exceptions seen
# AssertionError
# ModuleNotFoundError

start the project

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
```
Attention

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/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 in the assertion
```
7        self.assertFalse(False)
```
the test passes
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 seen in test_module_not_found_error.py
```
10# Exceptions seen
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

close the project

I close the file(s) I have open in the editor(s)
I click in the terminal and exit the tests with ctrl+c on the keyboard
I deactivate the virtual environment
```
deactivate
```
the terminal goes back to the command line, (.venv) is no longer on the left side
```
.../pumping_python/module_not_found_error
```
I change directory to the parent of module_not_found_error
```
cd ..
```
the terminal shows
```
.../pumping_python
```
I am back in the pumping_python directory

review

I ran a test for ModuleNotFoundError to practice making Python modules

code from the chapter

Do you want to see all the CODE I typed in this chapter?

what is next?

you have gone through a lot of information and know

Would you like to test AttributeError?

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AttributeError

dot notation