Readability
For this problem, you’ll implement a program that calculates the approximate grade level needed to comprehend some text, per the below.
$ python readability.py
Text: Congratulations! Today is your day. You're off to Great Places! You're off and away!
Grade 3
Background
According to Scholastic, E.B. White’s Charlotte’s Web is between a second- and fourth-grade reading level, and Lois Lowry’s The Giver is between an eighth- and twelfth-grade reading level. What does it mean, though, for a book to be at a particular reading level?
Well, in many cases, a human expert might read a book and make a decision on the grade (i.e., year in school) for which they think the book is most appropriate. But an algorithm could likely figure that out too!
So what sorts of traits are characteristic of higher reading levels? Well, longer words probably correlate with higher reading levels. Likewise, longer sentences probably correlate with higher reading levels, too.
A number of “readability tests” have been developed over the years that define formulas for computing the reading level of a text. One such readability test is the Coleman-Liau index. The Coleman-Liau index of a text is designed to output that (U.S.) grade level that is needed to understand some text. The formula is
index = 0.0588 * L - 0.296 * S - 15.8
where L is the average number of letters per 100 words in the text, and S is the average number of sentences per 100 words in the text.
Let’s write a program called readability that takes a text and determines its reading level. For example, if user types in a line of text from Dr. Seuss, the program should behave as follows:
$ python readability.py
Text: Congratulations! Today is your day. You're off to Great Places! You're off and away!
Grade 3
The text the user inputted has 65 letters, 4 sentences, and 14 words. 65 letters per 14 words is an average of about 464.29 letters per 100 words (because 65 / 14 * 100 = 464.29). And 4 sentences per 14 words is an average of about 28.57 sentences per 100 words (because 4 / 14 * 100 = 28.57). Plugged into the Coleman-Liau formula, and rounded to the nearest integer, we get an answer of 3 (because 0.0588 * 464.29 - 0.296 * 28.57 - 15.8 = 3): so this passage is at a third-grade reading level.
Walkthrough
Getting User Input
Let’s first write some code that just gets some text input from the user, and prints it back out. Specifically, implement in readability.py a main function that prompts the user with "Text: " and then prints that same text using print.
The program should behave per the below.
$ python readability.py
Text: In my younger and more vulnerable years my father gave me some advice that I've been turning over in my mind ever since.
In my younger and more vulnerable years my father gave me some advice that I've been turning over in my mind ever since.
Letters
Now that you’ve collected input from the user, let’s begin to analyze that input by first counting the number of letters in the text. Consider letters to be uppercase or lowercase alphabetical character, not punctuation, digits, or other symbols.
Add to readability.py, below main, a function called count_letters that takes one argument, text, and that returns the number of letters in that text.
def count_letters(text):
...
Then call that function in main so that, instead of printing out the text itself, your program now prints the number of letters in the text.
The program should now behave per the below.
$ python readability.py
Text: Alice was beginning to get very tired of sitting by her sister on the bank, and of having nothing to do: once or twice she had peeped into the book her sister was reading, but it had no pictures or conversations in it, "and what is the use of a book," thought Alice "without pictures or conversation?"
235 letters
Words
The Coleman-Liau index cares not only about the number of letters but also about the number of words in a sentence. For the purpose of this problem, we’ll consider any sequence of characters separated by a space to be a word (so a hyphenated word like "sister-in-law" should be considered one word, not three).
Add to readability.py, below main, a function called count_words that takes one argument, text, and that returns the number of words in that text.
def count_words(text):
...
Then call that function in main so that your program also prints the number of words in the text.
You may assume that a sentence:
- will contain at least one word;
- will not start or end with a space; and
- will not have multiple spaces in a row.
You are, of course, welcome to attempt a solution that will tolerate multiple spaces between words or indeed, no words!
The program should now behave per the below.
$ python readability.py
Text: It was a bright cold day in April, and the clocks were striking thirteen. Winston Smith, his chin nuzzled into his breast in an effort to escape the vile wind, slipped quickly through the glass doors of Victory Mansions, though not quickly enough to prevent a swirl of gritty dust from entering along with him.
250 letters
55 words
Sentences
The last piece of information that the Coleman-Liau formula cares about, in addition to the number of letters and words, is the number of sentences. You might first imagine that a sentence is just any sequence of characters that ends with a period, but of course sentences could end with an exclamation point or a question mark as well.
For this problem, you should consider any sequence of characters that ends with a . or a ! or a ? to be a sentence.
Add to readability.py, below main, a function called count_sentences that takes one argument, text, and that returns the number of sentences in that text.
def count_sentences(text):
...
Then call that function in main so that your program also prints the number of sentences in the text.
The program should now behave per the below.
$ python readability.py
Text: When he was nearly thirteen, my brother Jem got his arm badly broken at the elbow. When it healed, and Jem's fears of never being able to play football were assuaged, he was seldom self-conscious about his injury. His left arm was somewhat shorter than his right; when he stood or walked, the back of his hand was at right angles to his body, his thumb parallel to his thigh.
295 letters
70 words
3 sentences
Putting it All Together
Now it’s time to put all the pieces together! Recall that the Coleman-Liau index is computed using the formula:
index = 0.0588 * L - 0.296 * S - 15.8
where L is the average number of letters per 100 words in the text, and S is the average number of sentences per 100 words in the text.
If the resulting index number is 16 or higher (equivalent to or greater than a senior undergraduate reading level), your program should output "Grade 16+" instead of outputting an exact index number. If the index number is less than 1, your program should output "Before Grade 1".
How to Test Your Code
Try running your program on the following texts, to ensure you see the specified grade level. Be sure to copy only the text, no extra spaces.
One fish. Two fish. Red fish. Blue fish.(Before Grade 1)Would you like them here or there? I would not like them here or there. I would not like them anywhere.(Grade 2)Congratulations! Today is your day. You're off to Great Places! You're off and away!(Grade 3)Harry Potter was a highly unusual boy in many ways. For one thing, he hated the summer holidays more than any other time of year. For another, he really wanted to do his homework, but was forced to do it in secret, in the dead of the night. And he also happened to be a wizard.(Grade 5)In my younger and more vulnerable years my father gave me some advice that I've been turning over in my mind ever since.(Grade 7)Alice was beginning to get very tired of sitting by her sister on the bank, and of having nothing to do: once or twice she had peeped into the book her sister was reading, but it had no pictures or conversations in it, "and what is the use of a book," thought Alice "without pictures or conversation?"(Grade 8)When he was nearly thirteen, my brother Jem got his arm badly broken at the elbow. When it healed, and Jem's fears of never being able to play football were assuaged, he was seldom self-conscious about his injury. His left arm was somewhat shorter than his right; when he stood or walked, the back of his hand was at right angles to his body, his thumb parallel to his thigh.(Grade 8)There are more things in Heaven and Earth, Horatio, than are dreamt of in your philosophy.(Grade 9)It was a bright cold day in April, and the clocks were striking thirteen. Winston Smith, his chin nuzzled into his breast in an effort to escape the vile wind, slipped quickly through the glass doors of Victory Mansions, though not quickly enough to prevent a swirl of gritty dust from entering along with him.(Grade 10)A large class of computational problems involve the determination of properties of graphs, digraphs, integers, arrays of integers, finite families of finite sets, boolean formulas and elements of other countable domains.(Grade 16+)