Cycle over list indefinitely

Question

a = 1
b = 2
c = 3
x = a

def change_x():
    x = next??
    print("x:", x)

for i in range(10):
    change_x()

How can I cycle through a, b, c by calling change_x() indefinitely?

Output should be:

x: 2
x: 3
x: 1
x: 2
...

Answer 1

You could use cycle() and call next() as many times as you want to get cycled values.

from itertools import cycle

values = [1, 2, 3]
c = cycle(values)

for _ in range(10):
    print(next(c))

Output:

1
2
3
1
2
3
1
2
3
1

or as @chepner suggested without using next():

from itertools import islice

for i in islice(c, 10):
    print(i)

To get the same result.

Answer 2

You can use itertools.cycle, to cycle around the values in a, b and c as specified:

from itertools import cycle
for i in cycle([a,b,c]):
    print(f'x: {i}')

Output

x: 1
x: 2
x: 0
x: 1
x: 2
x: 0
x: 1
x: 2
x: 0
x: 1
...