for loop and list populating

[mepyyeti]

Ok I built a very basic caesar wheel...(w/out modules/classes). There was more trial/error than I care to admit . But, I came across something I couldn't figure out. Here is the relevant snippet.

base_wheel = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n',
'o','p','q','r','s','t','u','v','w','x','y','z']

new_wheel1 = []
new_wheel2 = []

spinner1 = random.randint(0,25)
spinner2 = spinner1

for b in base_wheel:
	new_wheel1.append(base_wheel[spinner1])
	spinner1 -= 1#no problem with decrementing
for b in base_wheel:
	new_wheel2.append(base_wheel[spinner2])

	#why does += 1 (below) go over range?  I am looping elements of base_wheel
	#loop is finite so spinner2 must also terminate
	spinner2 +=1

very puzzling to me... thx in advance...