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Python module structure for classes

I'm currently working on a project that I am structuring in the following manner:

.
├── example_app
│  ├── __init__.py
│  ├── app.py
│  ├── requirements.txt
│  └── classes
│  ├── ExampleClass1.py
│  ├── ExampleClass2.py
│  ├── __init__.py
└── tests
 └── test_app.py

Inside of classes/__init__.py I have defined a base class for all of the other "ExampleClasses" to inherit from. Then, inside of app.py I need to import all of these classes. However, this becomes very verbose, as I have to type:

from example_app.classes.ExampleClass1 import ExampleClass1
from example_app.classes.ExampleClass2 import ExampleClass2
...

Is there a way to structure this in a better way? Ideally I would like to keep each class in a separate file as they are not really similar to each other. I thought of importing all the classes inside of classes/__init.py but that does not seem right.

Note that although I only pictured 2 example classes there could be several (tens) of them so importing by hand is quite cumbersome and brittle.

Answer*

In my opinion, importing all the classes you want to expose from the subpackage `classes` inside its `__init__.py` is the way to go. In fact, that's what many top-tier Python libraries/frameworks do (see TensorFlow/Keras `layers` subpackage [here][1] and Python's `multiprocessing` subpackage [here][2]).

When doing that, however, you should probably follow [Google Python Style Guide][3] and:

> Use import statements for packages and modules only, not for
> individual classes or functions. Note that there is an explicit
> exemption for imports from the typing module.

In your case, it would translate to this:

`example_app/classes/__init__.py`:

```
from example_app.classes.ExampleClass1 import ExampleClass1
from example_app.classes.ExampleClass2 import ExampleClass2
```

`example_app/__init__.py`:

```
# ...
from example_app import classes
# ...
```

Some other `.py`:

```
from example_app import classes
ex1_instance = classes.ExampleClass1()
```

Or even better:

```
import example_app as ex
ex1_instance = ex.classes.ExampleClass1()
```


 [1]: https://github.com/tensorflow/tensorflow/blob/master/tensorflow/python/keras/layers/__init__.py
 [2]: https://github.com/python/cpython/blob/master/Lib/multiprocessing/__init__.py
 [3]: https://google.github.io/styleguide/pyguide.html

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Python module structure for classes

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