How to add a specific number to an index in python?

Question

I have a function in python that checks if the value of listy_poo[0] is a certain value. If it is, I need to skip index 1 and get the value of index 2.

My code:

def find():
    i = 0
    for e in listy_poo:
        if listy_poo[i] == 'value':
            print(listy_poo[i+2])
            i += 1

Clearly wrong, but is there something in python that accomplishes what I'm attempting?

UPDATE: I thought the problem was the syntax of listy_poo[i+2] but looking over the history has shown that I actually didn't save my change from when I attempted listy_poo[i]+2, which is wrong. Thanks for your help anyway, folks.

you want to do your same logic for 1st element as well (The logic that you perform for element with index 2 onwards)? — Anand S Kumar
– Anand S Kumar, Commented Oct 22, 2015 at 18:42
No, I need to skip the first element. The list is formatted in a way that guarantees that if 'value' is found, then exactly two elements over is another value which I need to extract. — jalyper
– jalyper, Commented Oct 22, 2015 at 18:44

Jeremy · Accepted Answer · 2015-10-22 19:04:28Z

1

Your code is close to working. If you change it to

def find(listy_poo, value_str):
    for i, e in enumerate(listy_poo):
        if e == value_str and i+2 < len(listy_poo):
            print(listy_poo[i+2])

The enumerate() function returns a tuple of the index of the given item in the list, and the item itself. I also added a check (i+2 < len(listy_poo)) to make sure you don't get an IndexError.

Looking at your description, I'm not positive this is doing what you want.

If you ran find(['a','b','c','d'],'b') then the function would print out d. That is, whenever it finds a match for the value, it moves over two spots in the list, and prints that value. Is that what you are going for?

answered Oct 22, 2015 at 19:04

Jeremy

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1 Comment

jalyper Over a year ago

Even though the bug I caught in my code fixed the basic functionality, this is a better solution for what I need. Thanks!

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