def double_chars(word):
    for j in range(len(word)):
        if word[j] == word[j:j 1]:
            chars_count = chars_count   1
    return chars_count

test_word = "Hello..world!"
print(double_chars(test_word))


Error: if word[j] == word[j 1]:
IndexError: string index out of range

I keep getting string index out of range on this function. I have tried different ways of indexing and slicing.

I am trying to return the count of character in a string that has double characters for example: bell--rung --> "ll" = 1, and "--" = 1. hence count of 2.

Am I doing something wrong in the code?

CodePudding user response：

The thing is that the range generates from 0 (inclusive) to the string's length (exclusive) which is ok for indexing, as string are 0-based indexed, but you don't only access current index, also the next one, so when reaching the last value of j, the [j 1] is one too far

def double_chars(word):
    chars_count = 0
    for j in range(len(word) - 1):
        if word[j] == word[j   1]:
            chars_count  = 1
    return chars_count

One-liner proposal, and another with zip

def double_chars(word):
    return sum(1 for j in range(len(word) - 1) if word[j] == word[j   1])

def double_chars(word):
    return sum(1 for ch_curr, ch_next in zip(word, word[1:]) if ch_curr == ch_next)