While loop inside While loop in python?

Question

I am a beginner in python.

The second loop only run for once, the first time only, but when the turn comes to the first loop and when e = e+1 - python skips the second loop!

Why?

The print order only work for once.

 items = [['.', '.', '.', '.', '.', '.'],
 ['.', 'O', 'O', '.', '.', '.'],
 ['O', 'O', 'O', 'O', '.', '.'],
 ['O', 'O', 'O', 'O', 'O', '.'],
 ['.', 'O', 'O', 'O', 'O', 'O'],
 ['O', 'O', 'O', 'O', 'O', '.'],
 ['O', 'O', 'O', 'O', '.', '.'],
 ['.', 'O', 'O', '.', '.', '.'],
 ['.', '.', '.', '.', '.', '.']]
i=0
e=0
while e < 6 :
 while i < 9 : #python run this loop only once, and never come back when e=e+1
 print items[i][e]
 i=i+1
 e=e+1 

• L_Church: Debugged this myself, changed the print to just print foo and added a print to the outer while to print bar, foo prints 9 times, bar prints 6 times after that's done. Is this not the expected behaviour
• Iris: i will try it , coz i haven't use 'print foo' before, i am using python 2.7 , thanks for this information :)
• L_Church: it doesn't do anything special i just used it so i could see how the loops worked

Answer 1

After the 'i' loop runs once, i will be set to 9 and will stay as 9 until you reset. so you can try to set it to 0 after e = e+1. A useful technique you can try is also printing the values of 'e' and 'i' to see where the loops gone wrong

items = [['.', '.', '.', '.', '.', '.'],
 ['.', 'O', 'O', '.', '.', '.'],
 ['O', 'O', 'O', 'O', '.', '.'],
 ['O', 'O', 'O', 'O', 'O', '.'],
 ['.', 'O', 'O', 'O', 'O', 'O'],
 ['O', 'O', 'O', 'O', 'O', '.'],
 ['O', 'O', 'O', 'O', '.', '.'],
 ['.', 'O', 'O', '.', '.', '.'],
 ['.', '.', '.', '.', '.', '.']]
i=0
e=0
while e <6 :
 while i <9 : 
 print items[i][e]
 print 'loop: i'+str(i)+'e'+str(e)
 i=i+1
 e=e+1
 i=0