PSET6 Readability "unsupported operand type(s) for *: 'float' and 'NoneType'"

Question

I'm getting "unsupported operand type(s) for *: 'float' and 'NoneType'" error for line 34: "s = (100 / words) * sentences".

Not sure what to make of this since count_sentences(text) does return a value.

Any help is greatly appreciated!

#import cs50

# Helper function to count letters only
def count_letters(text):
    letters = sum(c.isalpha() for c in text)
    return letters

"""Helper word and sentences counter function"""
def count_words(text):
    words = sum(s.isspace() for s in text)
    return words

def count_sentences(text):
    counter = 0
    for i in text:
        if i == ('!' or '?' or '.'):
            counter += 1
            print (counter)
            return counter



""" Readability - algorithm to assess writing level using Coleman-Liau index """

text = cs50.get_string("Text: ")  # Prompt user for text

""" Use helper methods to count letters, words, and sentences """
letters = count_letters(text)
words = 1 + count_words(text)
sentences = count_sentences(text)

""" Calculate letters and sentences per a hundred words """
l = (100 / words) * letters
s = (100 / words) * sentences

""" Coleman-Liau index index = 0.0588 * L - 0.296 * S - 15.8  """
grade = 0.0588 * l - 0.296 * s - 15.8

""" Cast to integer and round to nearest """
if grade > 16:
    print("Grade 16+")
    
elif grade < 1:
    print("Before Grade 1")
    
else:
    print(f"Grade: {int(round(grade))}")

Answer 1

Its because of an indentation problem. Unindent the the line return counter in the count_sentences() function twice i.e, it should have only a single indentation (of 4 spaces or a single tab). This should work:

import cs50

# Helper function to count letters only
def count_letters(text):
    letters = sum(c.isalpha() for c in text)
    return letters

"""Helper word and sentences counter function"""
def count_words(text):
    words = sum(s.isspace() for s in text)
    return words

def count_sentences(text):
    counter = 0
    for i in text:
        if i == ('!' or '?' or '.'):
            counter += 1
            print (counter)
    ################ Unindented the line below twice #######################
    return counter
    ########################




""" Readability - algorithm to assess writing level using Coleman-Liau index """

text = cs50.get_string("Text: ")  # Prompt user for text

""" Use helper methods to count letters, words, and sentences """
letters = count_letters(text)
words = 1 + count_words(text)
sentences = count_sentences(text)

""" Calculate letters and sentences per a hundred words """
l = (100 / words) * letters
s = (100 / words) * sentences

""" Coleman-Liau index index = 0.0588 * L - 0.296 * S - 15.8  """
grade = 0.0588 * l - 0.296 * s - 15.8

""" Cast to integer and round to nearest """
if grade > 16:
    print("Grade 16+")
    
elif grade < 1:
    print("Before Grade 1")
    
else:
    print(f"Grade: {int(round(grade))}")

Answer 2

It should not be difficult for you to check that the value of sentence is None, that is, your function count_sentences(text) is not returning anything, check the logic of your function to see what is wrong.