Question

Okay so basically, I need a bit of help with this very easy program I’ve threw together:

from graphics import *

def main():
win = GraphWin("Text Window", 400, 600)
options = ["Hello", "How", "Are", "You"]
x = 200
y = 20
for i in range(4):
    message = Text(Point(x,y), options[i])
    message.draw(win)
    y = y + 30

main()

Don’t worry about the ‘graphics’ module. It’s part of John Zelle’s Python book.
The point of this is I need to loop my range for 5 instead of 4, however, because ‘options’ is in [i], this particular program above will pull:

    0: Hello
    1: How
    2: Are
    3: You
    4: ???

However, if I change the 4 to a 5, it will look for a 4th item in the list however it doesn’t exist, so it will spit out an “IndexError: list index out of range”

What I want to achieve is, when the program reaches the end of the list, to loop back to the first (0) item in the list.

For example,

    for i in range(8):

Would pull out:

    0: Hello
    1: How
    2: Are
    3: You
    4: Hello
    5: How
    6: Are
    7: You

I have looked through this site and found some tools which haven’t lead to any success, this includes the ‘enumerate’ function which I don’t think will help.

If someone can shed some light on how to do this, it will be very welcome!
Hope I can do this without a nested loop aswell if this is at all possible.
Thanks you in advance for your help.

Answer 1

You can achieve this in one of two ways:

1. itertools.cycle

c = itertools.cycle(options)
for i in range(anyNumber):
    message = Text(Point(x,y), next(c))
    message.draw(win)
    y = y + 30

2. modulus

for i in range(anyNumber):
    message = Text(Point(x,y), options[i%len(options)])
    message.draw(win)
    y = y + 30

EDIT:

From the conversation in the comments:

If you want to print the contents of the list 4 times here are a couple of ways to accomplish this:

options = ["Hello", "How", "Are", "You"]
for i in range(4):
    for e,elem in enumerate(options):
        print("%d: %s" %(4*i+e, elem))

OR

options = ["Hello", "How", "Are", "You"]
for e,elem in enumerate(itertools.chain.from_iterable(itertools.repeat(options,4))):
    print("%d: %s" %(e, elem))

OR

options = ["Hello", "How", "Are", "You"]
for i in range(4):
    for j in range(len(options)):
        print("%d: %s" %(4*i+j, options[j]))