fun_fibonacci.py

import itertools
import operator

# https://joelgrus.com/2015/07/07/haskell-style-fibonacci-in-python/
def tee_fibs():
    yield 1
    yield 1
    fibs1, fibs2 = itertools.tee(tee_fibs())
    next(fibs2)  # Offset fibs2
    yield from map(operator.add, fibs1, fibs2)


def walrus_fibs():
    yield 1
    p = 0
    for n in walrus_fibs():
        yield p + (p := n)


def zip_prev(it):
    prev = next(it)
    for cur in it:
        yield prev, cur
        prev = cur


def fibs_zip_prev():
    yield 1
    yield 1
    yield from itertools.starmap(operator.add, zip_prev(fibs_zip_prev()))


def duplicate(it):
    prev = next(it)

    def i1():
        while True:
            yield prev

    def i2():
        nonlocal prev
        for x in it:
            prev = x
            yield x

    return i1(), i2()


def fibs_duplicate():
    yield 1
    yield 1
    i1, i2 = duplicate(fibs_duplicate())
    yield from map(operator.add, i1, i2)


def fib_zip():
    yield 1
    yield 1
    other_fibs = fib_zip()
    for prev, cur in zip(other_fibs, other_fibs):
        yield prev + cur
        yield prev + cur + cur


fibgens = [tee_fibs, walrus_fibs, fibs_zip_prev, fibs_duplicate, fib_zip]
for fibgen in fibgens:
    print(next(itertools.islice(fibgen(), 100, None)))