As usual, create a directory to hold today's files. All programs that you write today should be stored in this directory.
$ cd ~/cs120/labs $ mkdir lab21 $ cd lab21
Write a function is_substring(word_1, word_2). Your
function should use the in operator to determine if the
string word_1 is a substring
of word_2. word_1 is a substring
of word_2 if all of the characters of word_1
exist sequentially inside of word_2.
Write a function sum_ord(some_text). Your
function should use the for character in word style of
loop to sum the ordinal values of all of the characters
in some_text.
Some states require that legal documents not be written above a certain grade level. The Flesch-Kincaid grade level is a numeric score that indicates the minimum grade level in which an average student would be able to understand a text. Writing a function that computes the grade level of text requires being able to count the number of occurrences of certain characters.
In a file called reading_level.py write the
function compute_reading_level(text). The function
should return the Flesch-Kincaid grade level of the input text. The
Flesch-Kincaid grade level equation requires determining the number
of syllables in a sentence, which is very difficult for a program to
compute without a dictionary. The following equation is an
approximation to the Flesch-Kincaid grade level that does not use
syllables:
$$0.39\cdot(W/S)+11.8\cdot((L/3)/W)-15.59$$
Where \(W\) is the total number of words, \(S\) is the total number of sentences, and \(L\) is the total number of letters. Assume that all sentences end in a period, that all words are separated by a single space, and that all characters that are not a space or period are letters.
| Function Parameters | Expected Output |
|---|---|
| 'I do not like them Sam I am. I do not like green eggs and ham.' | -1.4075 |
| 'To be or not to be that is the question. Whether tis nobler in the mind to suffer the slings and arrows of outrageous fortune or to take arms against a sea of troubles and by opposing end them.' | 7.445769230769233 |
Determining the number of words requires counting the number
of space characters and determining the number of sentences
requires counting the period characters. Instead of writing
code to count each of these characters separately, write a
function count_character(character, text) that
counts the number of times character occurs
in text. The function should use an
accumulator variable to count and a for loop to traverse the
text one character at a time. For each character in the text
that is equal to input character, increment the counter.
Use the above function to determine the number of words and sentences. Determine the number of letters by using the length of the input text and the number of non-alphabetic characters. Before computing the reading level, test your code by printing the number of words, sentences, and letters on short examples.
The character count function was easy to write because it assumes that the input text only has alphabetic characters, single space characters, and period characters. This isn't very useful because most text does not conform to these restrictions. Modify the function so that it can work for any text. It should:
Most of us like to keep secrets. For example, I don't want you to know my credit card number. I'd rather you not be able to buy things with my money. However, communication over the Internet is like trying to shout in a crowded room. Everyone can hear what you are saying. So, to protect our valuable secrets, we rely on encryption schemes. Today, you are going to implement a simplistic encryption scheme known since Roman times: Caesar cipher.
In a file called caesar.py write the
function encrypt_word(a_word). This function takes a
single string as a parameter. Your function should return the
encryption of the a_word parameter.
Encryption in the Caesar schema relies on shifting letters in the alphabet. By default, this shift is 3 letters. So, \(a\) becomes \(d\), \(b\) becomes \(e\), etc. The only issue with this is at the end of the alphabet. The end of the alphabet wraps around to the front. So, \(x\) becomes \(a\), \(y\) becomes \(b\), and \(z\) becomes \(c\).
| Function Parameters | Expected Output |
|---|---|
| hello | -khoor |
| goodbye | jrrgebh |
The ord function gives you the ASCII
representation of a character. If you subtract
the ord('a') from this, you will get the
position in alphabet a character is.
You can use % to make the cyclic property of
the algorithm works. There are 26 letters in our alphabet.
The chr function takes an integer, and returns
to you the character that represents the ASCII value.
Encryption for Caesar is useful, but in order to talk to anyone
they need to be able to decrypt the Caesar encryption. Add a
function decrypt_word(a_word), which returns the
decryption of the a_word.