Question

In python (and some other languages) I have learned, that the name of a class should be written in small letters except for the first letter of each word, which should be a capital letter. Example:

class FooBar:
    ...

A class should go in a file, named the same as the class. In this example it would be a file foobar.py. If I want to import the class foo somewhere I have to do this:

from foobar import FooBar

This convention confuses me a little. My intuition tells me, that if the filename indicates a class, it should be written with the first letter in capitals, too, like FooBar.py. This doesn’t look pretty in file names. Perhaps someone could tell me what is the standard convention for this?

I hope I made my question understandable. 🙂

Answer 1

What you have presented is the standard convention.

Package and Module Names

Modules should have short, all-lowercase names. Underscores can
be used in the module name if it improves readability. Python packages
should also have short, all-lowercase names, although the use of underscores
is discouraged.

Since module names are mapped to file names, and some file systems are
case insensitive and truncate long names, it is important that module
names be chosen to be fairly short — this won’t be a problem on Unix,
but it may be a problem when the code is transported to older Mac or
Windows versions, or DOS.

When an extension module written in C or C++ has an accompanying Python
module that provides a higher level (e.g. more object oriented)
interface, the C/C++ module has a leading underscore (e.g. _socket).

Class Names

Almost without exception, class names use the CapWords convention.
Classes for internal use have a leading underscore in addition.

(Python Style Guide)

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See e.g.

from configparser import ConfigParser

(which, incidentally, was ConfigParser in Python 2.x but changed to be lowercase in 3.x).