Index out of range when printing adjacent letter

Question

I have string which is as follows below

stg = 'AVBFGHJ'

I want the adjacent letter to be printed as expected below

AV

VB

BF

FG

GH

HJ

J None

I tried below code but throws me error like Index out of Range

My code :

for i in range(len(stg)):
    print(stg[i],stg[i+1])

Yes, when `i` reaches the end of `len(stg)`, then what happens if you call `i+1`? — GAVD, Nov 14 '22 at 07:03
what about iterating NOT upt o the last letter? Or checkin if the letter is last then not adressing to the post-last letter? or something else? — Psytho, Nov 14 '22 at 07:07

score 1 · Accepted Answer · edited Nov 14 '22 at 07:11

1

This is meant to happen. You are accessing an index that is out of the range of the string.

If you really want to do it this way however, you can do something like this

stg = 'AVBFGHJ'
for i in range(len(stg)):
    if (i + 1) < len(stg):
        print(stg[i],stg[i+1])
    else:
        print(stg[i], None)

edited Nov 14 '22 at 07:11

JohnyCapo

answered Nov 14 '22 at 07:05

jspoh

mozway · Answer 2 · 2022-11-16T07:55:04.700

1

An easy pythonic approach is to use itertools.zip_longest:

from itertools import zip_longest

stg = 'AVBFGHJ'

for x in zip_longest(stg, stg[1:]):
    print(*x)

With python ≥3.10, you can use itertools.pairwise:

print(*(f"{a}{b}" for a,b in itertools.pairwise(stg)), sep='\n')

Thanks @chrslg for the remark.

Without itertoools, you can handle the last case separately:

for x in zip(stg, stg[1:]):
    print(*x)
print(stg[-1], None)

Output:

A V
V B
B F
F G
G H
H J
J None

edited Nov 16 '22 at 07:55

answered Nov 14 '22 at 07:28

mozway

What this stg[1:] does.. Please explain – nogoriv567 Nov 14 '22 at 10:42
@nogoriv567 it slices the string to remove the first character – mozway Nov 14 '22 at 12:15
Why not just `itertools.pairwise` if you use `itertools`? – chrslg Nov 16 '22 at 07:48
1

@chrslg you could but as it's a quite recent addition to `itertools` it's not yet available on all platforms – mozway Nov 16 '22 at 07:49
Yeah, but that a quite useful one :D `print(*(f"{a}{b}" for a,b in itertools.pairwise(stg)), sep='\n')` – chrslg Nov 16 '22 at 07:52
1

I added it for completeness – mozway Nov 16 '22 at 07:55

2 Answers2