How to fix "IndexError: string index out of range" error in python

Question

I recently started learning Python from a MOOC on Coursera. I'm trying to write a while loop that starts at the last character in the string and works its way backwards to the first character in the string, printing each letter on a separate line, except backwards.

I have written the code which is giving me the desired output but it's also giving me an error

"IndexError: string index out of range"

index = 0
fruit = "potato"
while index <= len(fruit) :
    index = index - 1
    letter = fruit[index] 
    print(letter)

 Traceback (most recent call last):
      File "strings_01.py", line 8, in <module>
        letter = fruit[index]
    IndexError: string index out of range

Thanks for your reply, I'm sorry if the above code looks stupid, I've just recently started to learn. I tried your recommendation and it doesn't work. It gives me the same error. — Prashant Gonga
– Prashant Gonga, Commented Jun 4, 2019 at 11:00

U13-Forward · Accepted Answer · 2019-06-04 11:07:33Z

1

Try using a different while loop condition:

index = 0
fruit = "potato"
while abs(index) < len(fruit):
    index = index - 1
    letter = fruit[index] 
    print(letter)

answered Jun 4, 2019 at 11:07

U13-Forward

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4 Comments

Prashant Gonga Over a year ago

Thank you, this works perfectly fine without any errors. Appreciate your help.

alec_djinn Over a year ago

Honestly, I prefer my answer since it doesn't need the abs() function call at every iteration.

U13-Forward Over a year ago

@PrashantGonga Happy to help :P

U13-Forward Over a year ago

@alec_djinn Well, okay, but OP preferred mine, also self-advertising isn't good

alec_djinn · Accepted Answer · 2019-06-04 11:09:47Z

1

This will work. Of course, it's just for the sake of learning, there are better ways to do that in Python.

fruit = "potato"
index = len(fruit) -1 #Python indexes starts from 0!
while index >= 0 :
    letter = fruit[index]
    print(letter)
    index -= 1 #decrease at the END of the loop!

Output:

o
t
a
t
o
p

answered Jun 4, 2019 at 11:09

alec_djinn

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Comments

Smart Manoj · Accepted Answer · 2019-06-04 10:58:47Z

0

fruit = "potato"
index = len(fruit)
while index > 0 :
    index = index - 1
    letter = fruit[index] 
    print(letter)

answered Jun 4, 2019 at 10:58

Smart Manoj

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1 Comment

Prashant Gonga Over a year ago

This code runs without any error but the output doesn't seem to be correct. Here is the output I've got. o t a t o p o There is an extra "o" added to the output at the end

Swaroop Maddu · Accepted Answer · 2019-06-04 11:06:45Z

0

This is what you are looking for

index = 0
fruit = "potato"
while index > -(len(fruit)) :
    index = index - 1
    letter = fruit[index]
    print(letter)

answered Jun 4, 2019 at 11:06

Swaroop Maddu

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Comments

Amazing Things Around You · Accepted Answer · 2019-06-04 11:16:34Z

0

Try this:

>>> fruit = "potato"
>>> fruit = fruit[::-1]
>>> fruit
'otatop'
>>> for letter in fruit:
...     print(letter)
...
o
t
a
t
o
p

Alternatively with while loop:

>>> fruit = "potato"
>>> fruit = fruit[::-1]
>>> fruit
'otatop'
>>>  index = 0
>>> while index < len(fruit):
...     print(fruit[index])
...     index+=1
...
o
t
a
t
o
p

edited Jun 4, 2019 at 11:16

answered Jun 4, 2019 at 11:03

Amazing Things Around You

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7 Comments

alec_djinn Over a year ago

The OP wants to use a while loop to do that.

Amazing Things Around You Over a year ago

@alec_djinn still what is the issue if I use for. But I will respect your comment and will edit answer.

Prashant Gonga Over a year ago

Thanks for your help, I need to write this code only using while loop

Amazing Things Around You Over a year ago

@PrashantGonga I have added the answer with while loop.

alec_djinn Over a year ago

@AmazingThingsAroundYou The issue is that the OP asked a solution involving a while-loop and you are answering with a for-loop. So, technically, it's a wrong answer. The code will work, but the answer doesn't fit the specs of the question.

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