class Range:
    def __init__(self, start, stop):
        self._current = start
        self._stop = stop
    
    def __iter__(self):
        return self
    
    def __next__(self):
        if self._current < self._stop:
            result = self._current
            self._current += 1
            return result
        else:
            raise StopIteration
            
for e in Range(0, 3):
    print(e)
            
i = Range(0, 3)
print(next(i))
print(next(i))
i = iter(i)
print(next(i))
print(next(i))

def range(start, stop):
    current = start
    while current < stop:
        yield current
        current += 1

        
g = range(0, 3)
for e in g:
    print(e)

g = range(0, 3)
print(next(g))
print(next(g))
print(next(g))
print(next(g))

def range(start, stop):
    current = start
    while current < stop:
        reset = yield current
        if reset is not None:
            current = reset - 1
        current += 1

        
g = range(0, 3)
print(next(g))
print(next(g))
print(g.send(0))
print(next(g))

def range(start, stop):
    current = start
    while current < stop:
        reset = yield current
        if reset is not None:
            current = reset - 1
        current += 1

def two_ranges(start, stop):
    for x in range(start, stop):
        yield x
    for x in range(start, stop):
        yield x
        
g = two_ranges(0, 3)
print(next(g))
print(next(g))
print(next(g))
print(next(g))
print(next(g))
print(next(g))

g = two_ranges(0, 3)
print(next(g))
print(next(g))
print(g.send(-1))
print(next(g))
print(next(g))
print(next(g))
print(next(g))

def range(start, stop):
    current = start
    while current < stop:
        reset = yield current
        if reset is not None:
            current = reset - 1
        current += 1

def two_ranges(start, stop):
    yield from range(start, stop)
    yield from range(start, stop)
        
g = two_ranges(0, 3)
print(next(g))
print(next(g))
print(next(g))
print(next(g))
print(next(g))
print(next(g))

g = two_ranges(0, 3)
print(next(g))
print(next(g))
print(g.send(-1))
print(next(g))
print(next(g))
print(next(g))
print(next(g))

g = (x for x in [1, 2, 3])
print(next(g))
print(next(g))
print(next(g))
print(next(g))

g = (x * x for x in [1, 2, 3])
for e in g:
    print(e)

g = (x * x for x in range(10) if x % 2 == 0)
list(g)

g = (x * y for x in range(3) for y in range(4))
list(g)

a = [x * x for x in [1, 2, 3]]
a

s = {x * x for x in [1, 2, 3]}
s

d = {x: x * x for x in [1, 2, 3]}
d

import itertools


i = itertools.chain(range(3), range(5), range(2))
for e in i:
    print(e)

i = itertools.combinations(range(4), 3)
list(i)

i = itertools.permutations(range(4), 3)
list(i)

i = itertools.cycle(range(4))
print(next(i))
print(next(i))
print(next(i))
print(next(i))
print(next(i))
print(next(i))
print(next(i))
print(next(i))
print(next(i))

i = itertools.product("abcdefgh", range(1, 9))
list(i)