Clarifying the magic method __new__

Question

python
class ReversedStr(str):
  def __new__(*args, **kwargs):
    self = str.__new__(*args, **kwargs)
    self = self[::-1]
    return self

Kenneth says in the video that __new__ is a class method. However he omits the cls name. Why is this?
https://docs.python.org/3/reference/datamodel.html#object.new
In the documentation, it states that __new__, as it's first parameter, takes the class of which an instance was requested as its first argument.  The remaining arguments are those passed to the object constructor expression (the call to the class).
So if the first argument is suppose to some class, why is this first argument in Kenneth's code *args, or in other words a tuple?

Chris Freeman · Accepted Answer

Great question! 
You are correct, in that, the first argument of the __new__ method should be the class. In the documentation link (https://docs.python.org/3/reference/datamodel.html#object.__new__) you included, the declaration formation is object.__new__(cls[, ...]).  
In Kenneth's code, by using (*args, **kwargs), it is effectively the same as (cls, *args[1:], **kwargs) where  the first positional argument is used for the class. Since the *args are passed through to the subsequent __new__() call, it works, but it is not explicit. So it is fine to use cls as the first argument.
One other correction, as noted in the docs, "__new__() is a static method (special-cased so you need not declare it as such)...." Normally, a static method does not have a class cls or instance self as the first argument. But __new__ does have a class as it's first argument.
Perhaps Kenneth's style of omitting the cls is to follow form of a regular static method parameter format.
Post back if you have more questions. Good luck!!

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Clarifying the magic method new

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Chris Freeman

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