string index out of range error in for loop

Question

I am trying to make a program that searches a string for 'bob' and prints the amount of times it appears. Here is the code:

s = 'mbobobboobooboo'
numbob = 0
for i in range(len(s) ) :
    u = s[i] 
    if u == 'o':
        g = i
        if g != 0 and g != len(s) :
            if (s[g+1]) == 'b' and (s[g-1]) == 'b': #this line is the problam
                numbob += 1
                print("Number of times bob occurs is: " +str(numbob) )

I am getting the string index out of range error and i cant seem to fix it. any suggestions

This seems to be a duplicate of: http://stackoverflow.com/questions/1155617/count-occurrence-of-a-character-in-a-string Which provides a much nicer way to do what you're doing. :) — Kieran, Sep 20 '16 at 18:32
Note that `'bobob'.count('bob') == 1`, not 2 as one might hope. — BallpointBen, Sep 20 '16 at 21:16

score 3 · Answer 1 · edited Sep 20 '16 at 19:58

3

Use

for i in range(len(s)-1)

or

g!=len(s)-1

len() gives you the total number of characters, which will be the index of the character after the last one since indexing starts at 0.

You can get rid of the if g!=0 and g!=len(s) part all together if you use

for i in range(1,len(s)-1)

edited Sep 20 '16 at 19:58

Saeid

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answered Sep 20 '16 at 18:31

SilentLupin

658
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it worked! thank you for the quick answer, i can't stress that enough – jon smith Sep 20 '16 at 18:34
1

@sudomakeinstall2 Thanks for the edit. It looks much nicer now. :) – SilentLupin Sep 20 '16 at 20:01

score 0 · Answer 2 · answered Sep 20 '16 at 18:31

When you make your condition :

if (s[g+1]) == 'b' and (s[g-1]) == 'b':

At the last element of your string, it is impossible to do s[g+1] because it is out of the string.

So you have to finish your loop just before the end. Like this for exemple :

for i in range(len(s)-1) :

score 0 · Answer 3 · answered Sep 12 '18 at 10:00

my solution would more easy than your. instead of divide letters 'b' 'o' 'b' . slice string s

countbob=0
bob='bob'
for i in range(len(s)):
       bob2=s[i:i+3]
       if bob2 == bob:
               countbob +=1
print ("Number of times bob occurs is: " + str(countbob))

string index out of range error in for loop

3 Answers3