There is no such method for sequences in python. So you are not able to call @list.length()@, @dict.length()@, @tuple.length()@ etc.
The official explanation is that it is more readable but i don't believe that. If you are creating your own Classes you can add lenght() method and still have builtin @len()@ support.
To get length of a sequence use builtin len() function:
len([0,1,2,3,4]) # returns 5
When you call @len()@ function it calls builtin @sequence.len()@ method. So if you want to create your own object with len() support you have to add your own @len()@ method:
class MyObject: def __len__(self): return 100 x = MyObject() len(x) # returns 100