Reverse the 5-letter words in a phrase

# 1. Defining a function for finding the spacebar characters in a word/phrase
def findSpacesInString(str):
    # The next list will have the indexes of spacebar-chars in my phrase-string
    spacesList = [-1]
    for i in range(0, len(str)):
        if str[i] == ' ':
            spacesList.append(i)

    # If the last character of my string "str" is not the spacebar-char, then I will
    # add the (last index + 1) in my spacebar list
    if str[len(str)-1] != ' ':
        spacesList.append(len(str))

    return spacesList


# 2. Defining a function that breaks the phrase in single words
def findSingleWords(str):
    spacesList = findSpacesInString(str)
    words = []
    word = ""
    for i in range (0, len(spacesList)-1):
        # Example: word = "partnership" ---->  word[2:6] = "rtne"
        word = str[(spacesList[i]+1) : spacesList[i+1]]
        words.append(word)

    return words


# 3. Defining a function that creates the final string/phrase
def reverseWhenNecessary(str):
    words = findSingleWords(str)                # words = list with strings (every string is a word)
    finalString = ""
    for word in words:# 1. Defining a function for finding the spacebar characters in a word/phrase
def findSpacesInString(str):
    # The next list will have the indexes of spacebar-chars in my phrase-string
    spacesList = [-1]
    for i in range(0, len(str)):
        if str[i] == ' ':
            spacesList.append(i)

    # If the last character of my string "str" is not the spacebar-char, then I will
    # add the (last index + 1) in my spacebar list
    if str[len(str)-1] != ' ':
        spacesList.append(len(str))

    return spacesList


# 2. Defining a function that breaks the phrase in single words
def findSingleWords(str):
    spacesList = findSpacesInString(str)
    words = []
    word = ""
    for i in range (0, len(spacesList)-1):
        # Example: word = "partnership" ---->  word[2:6] = "rtne"
        word = str[(spacesList[i]+1) : spacesList[i+1]]
        words.append(word)

    return words


# 3. Defining a function that creates the final string/phrase
def reverseWhenNecessary(str):
    words = findSingleWords(str)                # words = list with strings (every string is a word)
    finalString = ""
    for word in words:
        # If length >=5, I will put in my string my word BUT REVERSED
        # and then I will also add a spacebar/char, because it's another single word following
        if len(word) >= 5:
            # When I reverser a string, such as: str= "hello", I write:
            finalString += word[::-1] + ' '
        else:
            finalString += word + ' '

        # At the end of this process, I will have at the end one more spacebar/character(' ')
        finalString = finalString[0:len(finalString)-1]
        return finalString


# MAIN FUNCTION OF THE PROGRAMME
phrase = "Hello my friend"
print(findSpacesInString(phrase))
print(findSingleWords(phrase))
print(reverseWhenNecessary(phrase))
        # If length >=5, I will put in my string my word BUT REVERSED
        # and then I will also add a spacebar/char, because it's another single word following
        if len(word) >= 5:
            # When I reverser a string, such as: str= "hello", I write:
            finalString += word[::-1] + ' '
        else:
            finalString += word + ' '

        # At the end of this process, I will have at the end one more spacebar/character(' ')
        finalString = finalString[0:len(finalString)-1]
        return finalString


# MAIN FUNCTION OF THE PROGRAMME
phrase = "Hello my friend"
print(findSpacesInString(phrase))
print(findSingleWords(phrase))
print(reverseWhenNecessary(phrase))