Python While반복문

i = 0
a = [1, 2, 3, 4]
s = 3
# while문 이용
while i < len(a):
    if a[i] == s:
      print(s, 'found in list')
      break
    i += 1
else:
    print(s, 'not found in list')
# for문 이용
for p in a:
    if s == p:
        print(s, 'found in list')
        break
else:
    print(s, 'not found in list')

# d, c, b, a -> LIFO
list1 = ['a', 'b', 'c', 'd']
while list1:
  print(list1.pop())