Why are sorted () and reverseed () are built-in functions and not sequence methods?

Question

Now I'm moving into Python 3.3, and I'm wondering why some functions (for example sorted(), reversed()) for managing collections / iterable are built-in, but some of them are implemented as methods of collection objects? I can add an item to the list using the method append(), but in order to get its length, I have to use the built-in function len(). It seems inconsistent to me, but I think I just missed some point in the new language.

Answer 1

The short answer is that these decisions were made for human reasons, and not for technical reasons.

Justification len()versus obj.length() explained by Guido van Rossum (Python Benevolent Dictator For Life):

First of all, I chose len (x) for x.len () for HCI reasons (def __len__()came much later). There are actually two related reasons: and HCI:

(a) For some operations, prefix notation only reads better than postfix - prefix (and infix!) operations have a long tradition in mathematics that loves notes where visual effects help the mathematician think about a problem. Compare the ease with which we rewrite a formula such as x * (a + b) to x * a + x * b, to be awkward at doing the same using raw OO notation.

(b) , len (x), , -. : - , - - . , x.len(), , x - - , , len(). , , , , get() keys() -, , write().

, sorted() reversed() :

, ; , , . , max, sum, map, any, in others, , , .