有人可以用正确的方法指导我在以下代码中进行迭代吗

Question

This is a question from Python Challenge: Double letters

The goal of this challenge is to analyze a string to check if it contains two of the same letter in a row. For example, the string "hello" has l twice in a row, while the string "nono" does not have two identical letters in a row.

Define a function named double_letters that takes a single parameter. The parameter is a string. Your function must return True if there are two identical letters in a row in the string, and False otherwise.

I tried below code:

def double_letters(word):
    for i in range(len(word)+1):
        if word[i] == word[i+1]:
            return True
        else:
            return False

double_letters('hello')

The problem here is: when i return false at the end of my function, it works perfectly fine for a true statement (eg 'Hello'), but doesn't work for False statement (eg 'Master'), i get an error instead: IndexError: string index out of range

Answer 1

I was using a wrong range for the 'for loop'. Since, my if statement uses index+1, so my code was throwing an error as out of range.. Below is the correct code:

def double_letters(word):
    for i in range(len(word)-1):
        if word[i] == word[i+1]:
            return True
    return False     
double_letters('hello')

Answer 2

A very basic solution for this:

def double_letters(word: str):
    prev_letter = None
    for letter in list(word):
        if prev_letter is None:
            prev_letter = letter
            continue
        if letter == prev_letter:
            return True
        prev_letter = letter
    return False