IndexError：我的函数的字符串索引超出范围

Question

I am trying to create a function which allows me to split up a string and add each word to a list then return the words which begin with a certain letter in that list without using the .split() command. The first part of the function (splitting the string and adding each word to a list) works perfectly fine. The issue is when trying to return the values within that list which begin with a certain letter. Here is my code:

def getWordsStartingWith(text, letter):
    split_text = [] #This is where each word is appeneded to.
    text_addition = ""  #This is where the letters from the string are added.
    number = 0
    gWSW = []
    for str in text:
        if str == ' ' or str == "'": # Checks to see whether the letter is a space or apostrophy.
            split_text.append(text_addition)
            text_addition = "" #If there is, then the letters collected so far in text_addition are apended to the list split_text and then cleared from text_addition
        else:
            text_addition += str #If not, then the letter is added to the string text_addition.

    while number < len(split_text)-1:
        if split_text[number][0] == letter:
            gWSW.append(split_text[number])
            number += 1
        else:
            number += 1
    else:
        return gWSW

The issue is with the line

if split_text[number][0] == letter:

where it returns an IndexError as stated in the title. I'm pretty sure it has something to do with the [number] variable being used but not sure what to do.

Answer 1

Like the comments to your question states you have a couple of problems there, first you are dropping the last word, you could fix that with:

    else:
        text_addition += str #If not, then the letter is added to the string text_addition.

    # Avoid dropping last word
    if len(text_addition):
        split_text.append(text_addition)

    while number < len(split_text)-1:
        if split_text[number][0] == letter:

Then I think your IndexError problem comes when you have two "spaces", in that situation you are adding an empty string and since it doesn't have any char [0] is indexError. You could fix that with:

    for str in text:
        if str == ' ' or str == "'": # Checks to see whether the letter is a space or apostrophy.
            if text_addition:
                # Here we avoid adding empty strings
                split_text.append(text_addition)
            text_addition = "" #If there is, then the letters collected so far in text_addition are apended to the list split_text and then cleared from text_addition
        else:
            text_addition += str #If not, then the letter is added to the string text_addition.

That it's just to answer your question.

PD: I little improvement on the last part would be to do:

    result = []
    for str in split_text:
        if str.startswith(letter):
            result.add(str)
    return result