Organizing Python classes in modules and/or packages

I like the Java convention of having one public class per file, even if there are sometimes good reasons to put more than one public class into a single file. In my case I have alternative implementations of the same interface. But if I would place them into separate files, I'd have redundant names in the import statements (or misleading module names):

import someConverter.SomeConverter

whereas someConverter would be the file (and module) name and SomeConverter 开发者_运维百科the class name. This looks pretty inelegant to me. To put all alternative classes into one file would lead to a more meaningful import statement:

import converters.SomeConverter

But I fear that the files become pretty large, if I put all related classes into a single module file. What is the Python best practise here? Is one class per file unusual?

A lot of it is personal preference. Using python modules, you do have the option to keep each class in a separate file and still allow for import converters.SomeConverter (or from converters import SomeConverter)

Your file structure could look something like this:

* converters
     - __init__.py
     - baseconverter.py
     - someconverter.py
     - otherconverter.py

and then in your __init__.py file:

from baseconverter import BaseConverter
from otherconverter import OtherConverter

Zach's solution breaks on Python 3. Here is a fixed solution.

A lot of it is personal preference. Using python modules, you do have the option to keep each class in a separate file and still allow for import converters.SomeConverter (or from converters import SomeConverter)

Your file structure could look something like this:

* converters
     - __init__.py
     - baseconverter.py
     - someconverter.py
     - otherconverter.py

and then in your __init__.py file:

from converters.baseconverter import BaseConverter
from converters.otherconverter import OtherConverter

The above solutions are good, but the problem with importing modules in __init__.py is that this will cause all the modules to be loaded twice(inefficient). Try adding a print statement at the end of otherconverter.py and run otherconverter.py. (You'll see that the print statement is executed twice)

I prefer the following. Use another package with name "_converter" and define everything there. And then your "converters.py" becomes the interface for accessing all public members

* _converters
     - __init__.py
     - baseconverter.py
     - someconverter.py
     - otherconverter.py

*  converters.py

where converters.py is

from _converters.someconverter import SomeConverter
from _converters.otherconverter import OtherConverter
...
...
...
converters = [SomeConverter, OtherConverter, ...]

And as the previous solutions mentioned, it is a personal choice. A few practices involve defining a module "interace.py" within the package and importing all public members here. If you have many modules to load, you should choose efficiency over aesthetics.