# CPSC120BFundamentals of Computer Science I

## Lab 19

Strings

Write a function called append_exclamation(a_phrase), which takes a string as a parameter. This function should return a string, which is simply a_phrase with an exclamation point appended to the end.

Write a function called get_extents(a_phrase), which takes a string as a parameter. This function should return a string, which contains only the first and last characters from a_phrase.

Passwords are possibly the most important way that individuals can ensure their own safety on the Internet. However, it is also typically the easiest thing for a hacker to figure out, or to get their hands on. This is simply because most Internet users choose incredibly weak passwords. The easiest way to get around this issue to to use a randomly generated password.

#### Details

Write a function called generate_password(size), which takes a positive integers as a parameter. Your program should return a string of lower case letters of the specified size. This function should randomly choose the lower case letters in the returned string.

Make sure you test your program well. How many test cases do you need? Make sure you follow all of the course's coding conventions.

#### Example Execution

$python3 password_generation.py How long do you want your password? 5 neolp$ python3 password_generation.py
wigmnhgqwn


#### Hint

• Since you only need to generate lower case passwords, you can use the string.ascii_lowercase constant to access letters from that range.

• You can use the random module to generate random numbers. Since we know we are generating lower-case characters, you need to generate a random number to use as an index in the string.ascii_lowercase string.

• Since you know how many characters you want, you should use a for loop for this activity. You are also using the accumulator pattern again, but with strings this time.

### Challenge

Even random strings of lowercase characters are pretty easy to break. A better program would randomly decide to include some uppercase letters as well. Alter your function so that it will sometimes include uppercase letters in the generated passwords. Make sure the parameter used to determine how often an uppercase character is used is well documented and easily altered.

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.

#### Details

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.

#### Sample Test Cases

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

#### Hint

• 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.

### Challenge

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:

1. allow any number of space, tab, or new line characters between words and sentences.
2. allow sentences to end in a period, question mark, or exclamation point.
3. ignore all non-alphabetic characters when counting letters.

### Submission

Please show your source code and run your programs for the instructor or lab assistant. Only a programs that have perfect style and flawless functionality will be accepted as complete.