If the convention in Python is to capitalize classes, why then is list() not capitalized? Is it not a class?

Question

Often when I see class definitions class Foo:, I always see them start with upper case letters.

However, isn't a list [] or a dict {} or some other built-in type, a class as well? For that matter, everything typed into the Python's IDLE which is a keyword that is automatically color coded in purple (with the Window's binary distribution), is itself a class, right?

Such as spam = list()

spam is now an instance of a list()

So my question is, why does Python allow us to first of all do something like list = list() when nobody, probably, does that. But also, why is it not list = List()

Did the developers of the language decide not to use any sort of convention, while it is the case that most Python programmers do name their classes as such?

Answer 1

Yes, uppercase-initial classes are the convention, as outlined in PEP 8.

You are correct that many builtin types do not follow this convention. These are holdovers from earlier stages of Python when there was a much bigger difference between user-defined classes and builtin types. However, it still seems that builtin or extension types written in C are more likely to have lowercase names (e.g., numpy.array, not numpy.Array).

Nonetheless, the convention is to use uppercase-initial for your own classes in Python code.