Purpose of return self python

Question

I have a problem with return self

class Fib: 
    def __init__(self, max):
        self.max = max
    def __iter__(self): 
        self.a = 0
           


        

Answer 1

This is needlessly complex code. Pay little attention to it. There's no reason on earth to implement it this way.

That being said, what it does is this:

class Fib: 

    """Implements the Fibonacci sequence."""

    def __init__(self, max_):
        self.max = max_

    def __iter__(self):
        """Initializes and returns itself as an iterable."""

        self.a = 0
        self.b = 1
        return self

    def __next__(self):
        """What gets run on each execution of that iterable."""

        fib = self.a
        if fib > self.max:
            raise StopIteration
        self.a, self.b = self.b, self.a + self.b  # increment
        return fib

This is all much easier to express as:

def fib(max_):
    a, b = 0, 1
    while b <= max_:
        out = a
        a, b = b, a+b
        yield out

Examples:

>>> fib_obj = Fib(20)
>>> for n in fib_obj:
...     print(n)

>>> for n in Fib(20):
...     print(n)

>>> for n in fib(20):
...     print(n)
# all give....
0
1
1
2
3
5
8
13