How to make two iteration in for loop using for-in syntax

Question

Assume I have a list and I am looping in it with for-in syntax. Can this be done with for-in syntax or better question would be what is the most pythonic way to do this?

l= ["ok", "item1", "nope", "item2", "nope", "item3", "ok", "item4"]
for item in l:
    if item == "ok":
        print(item + ": " + ... ) # Where ... should be next item

I want this code prints out something like

ok: item1
ok: item4

edit: A more clear list example would be like accourding to comments:

l= ["ok", "item1", "nope", "item2", "somevalue","nope", "item3", "ok", "item4"]

Is it guaranteed that the list has an even number of elements and it alternates between ok/nope and value? — user202729, Aug 16 '19 at 12:00
nope it is not guarenteed. What guarenteed is item always comes after ok/nope . Let me edit question. — erondem, Aug 16 '19 at 12:05
Possible duplicate of [Iterate a list as pair (current, next) in Python](https://stackoverflow.com/questions/5434891/iterate-a-list-as-pair-current-next-in-python) — user202729, Aug 16 '19 at 12:07

score 1 · Accepted Answer · answered Aug 16 '19 at 12:02

l= ["ok", "item1", "nope", "item2", "nope", "item3", "ok", "item4"]
for index, item in enumerate(l):
    if item == "ok":
        print(f"{item}: {l[index + 1]}")

using enumerate() you can get the value and the index of the current item from your list. If the value of the current item == "ok", then print the next item from the list via index + 1.

score 0 · Answer 2 · answered Aug 16 '19 at 12:22

One possibility is use zip() method and slicing:

l= ["nope", "ok", "item1", "nope", "item2", "somevalue","nope", "item3", "ok", "item4"]

for val1, val2 in zip(l[::1], l[1::1]):
    if val1 == 'ok':
        print('{} : {}'.format(val1, val2))

Prints:

ok : item1
ok : item4

score 0 · Answer 3 · answered Aug 16 '19 at 13:08

l= ["ok", "item1", "nope", "item2", "nope", "item3", "ok", "item4"]
for itemno in range(len(l)):
    if l[itemno] == "ok":
        print(l[itemno] + ": " +l[itemno+1] )

i think no need to use zip or enumerate as they take some computations. so to making problem simple, just think simple.

How to make two iteration in for loop using for-in syntax

3 Answers3