How to get the previous element when using a for loop? [duplicate]

Answer 1

Just keep track of index using enumerate and get the previous item by index

li = list(range(10))

for i, item in enumerate(li):
    if i > 0:
        print(item, li[i-1])

print("or...")

for i in range(1, len(li)):
    print li[i], li[i-1]

Output:

1 0
2 1
3 2
4 3
5 4
6 5
7 6
8 7
9 8
or...
1 0
2 1
3 2
4 3
5 4
6 5
7 6
8 7
9 8

Another alternative is to remember the last item, e.g.

last_item = None
for item in li:
    print(last_item, item)
    last_item = item