Is arr.__len__() the preferred way to get the length of an array in Python?

Question

In Python, is the following the only way to get the number of elements?

arr.__len__()

If so, why the strange syntax?

Answer 1

The way you take a length of anything for which that makes sense (a list, dictionary, tuple, string, ...) is to call len on it.

l = [1,2,3,4]
s = 'abcde'
len(l) #returns 4
len(s) #returns 5

The reason for the "strange" syntax is that internally python translates len(object) into object.__len__(). This applies to any object. So, if you are defining some class and it makes sense for it to have a length, just define a __len__() method on it and then one can call len on those instances.