Python Slicing 'bob' in s

python slice

11,304

Solution 1

Here, try this, handcrafted :)

for i, _ in enumerate(s): #i here is the index, equal to "i in range(len(s))"
    if s[i:i+3] == 'bob': #Check the current char + the next three chars.
        bob += 1
print('Number of times bob occurs is: ' + str(bob))

Demo

>>> s = 'gfdhbobobyui'
>>> bob = 0
>>> for i, v in enumerate(s): #i here is the index, equal to "i range(len(s))"
    if s[i:i+3] == 'bob': #Check the current char + the next two chars.
        bob += 1


>>> bob
2

Hope this helps!

Solution 2

x is a number, it can't be equal to 'bob'. That's why it always output 0.

You should use x in order to get a substring of s:

bob = 0
for x in range(len(s) - 2):
    if s[x:x+3] == 'bob':
        bob += 1

You can also use enumerate.

Solution 3

s = 'gfdhbobobyui'
bob = 0
for x in range(len(s)):
     if s[x:x+3] == 'bob':  # From x to three 3 characters ahead.
         bob += 1
print('Number of times bob occurs is: ' + str(bob))

Working example.

But the best way is this, however it does not work with overlapping strings:

s.ount('bob')

11,304

Author by

Patrick Hayes

Updated on November 25, 2022

Comments

Patrick Hayes over 1 year
```
    s = 'gfdhbobobyui'
    bob = 0
    for x in range(len(s)):
         if x == 'bob':
             bob += 1
    print('Number of times bob occurs is: ' + str(bob))
```
Attempting to write a code that will count the amount of times 'bob' appears in s, but for some reason this always outputs 0 for number of 'bob'.
- JadedTuna over 10 years
  
  Ahh why noone uses regex? len(re.findall("(?=bob)", "gfdhbobobyui"))
- aIKid over 10 years
  
  @Vik2015 I don't know why, but i studied regex for a few pages and i found out that i hate it..
aIKid over 10 years

actually, since you're only comparing the string, len(s) is sufficient.
aIKid over 10 years

Also, str.count() doesn't work with overlapping occurences :)
Games Brainiac over 10 years

@aIKid You'll gen an index error.
aIKid over 10 years

Nope. I didn't. See my example, i copy pasted it.
Games Brainiac over 10 years

@aIKid Well thats strange, it seems that slicing out of bounds raises no exception.
aIKid over 10 years

Yep. I'm curious of that too actually HAHAHA. But it just works.
Patrick Hayes over 10 years

Thank you, what is enumerate?
Maxime Chéramy over 10 years

@GamesBrainiac Yep, there is no index error. However, why stopping at len(s)-1 ?
aIKid over 10 years

It returns a tuple of the index and the value. So i'm catching it with two variables, v is for the current value, and i is for the current index.
aIKid over 10 years

For details, see the docs :)
aIKid over 10 years

@Maxime since if you're on the -1th index, it's impossible to have a three character word, isn't it? =)
Patrick Hayes over 10 years

OK thank you that makes since!
Maxime Chéramy over 10 years

@alKid exactly. So you can stop even earlier ;). That's what I'm saying.
Patrick Hayes over 10 years

I'll check that out appreciate it!
Maxime Chéramy over 10 years

I'd suggest you to write for i, _ in enumerate(s) since you don't use v. Also, enumerate might be slightly slower than using range(len(s)) and you also do 2 extra unnecessary iterations.
Maxime Chéramy over 10 years

@GamesBrainiac You have updated your answer but forgot to change the code on Ideone which was incorrect (didn't work with gfdhbobob because of the -3 instead of -2).
aIKid over 10 years

@Maxime Thanks. Edited