Capitalizing the first letter of each sentence in Python

Here is my code:

def fix_capitalization(usrStr):

    newString = ''

    wordList = []

    numLetters = 0

    for s in usrStr.split('. '):

        if s[0].isupper():

            s = s.capitalize()

            s = s.replace(' i ', " I ") 

            wordList.append(s)

        if s.islower():

            s = s.capitalize()

            s = s.replace(' i ', " I ") 

            wordList.append(s)

            numLetters += 1



        if s[0].islower():

            s = s.capitalize()

            s = s.replace(' i ', " I ") 

            wordList.append(s)

            numLetters += 1 







    newString = '. '.join(wordList)

    return newString, numLetters

The string being passed in is:



Note that there are 4 spaces before . The result that I want is:



but I get:



I know that isn't being capitalized because I split on and that sentence has more than one space after the period, but I'm not sure how I can fix this or if there's a better way to go about what I'm doing. Any help would be greatly appreciated.