CPSC120
Fundamentals of Computer Science

Substring

Write the function substring(text: str, start: int, end: int) -> str that returns a contiguous subsequence of characters in a string. The parameter text is a string, and the parameters start and end are non-negative integers. The function should return a copy of the characters from text between start and end. The substring should include the character at the index start, but it should exclude the character at the index end. Assume that both start and end are between 0 and the length of text and that start is less than end. The function should assert that start and end are valid indices.

Test Cases

import test

def substring(text: str, start: int, end: int) -> str:
    # Put your code here

def main() -> None:
    test.equal(substring("hello", 1, 4), "ell")
    # Put more test cases here
    return None

main()

Password Generation

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 get their hands on. This is simply because most internet users choose incredibly weak passwords. The easiest way to solve this is to use a randomly generated password.

Details

Write the Python function generate_password(size: int) -> str that returns a string of random lowercase letters. It should be possible for the generated password to contain any letter. The parameter size is a positive integer and is the number of characters in the returned password.

Example

The code:

print(generate_password(5))
print(generate_password(10))

Might print:

Hint

Challenge

Even random strings of lowercase characters are pretty easy to break. A better program would also include uppercase letters and digits. Alter your function so that it is guaranteed to have at least 1 lowercase letter, 1 upper-case letter, and 1 digit. Note, the location of the required characters should still be completely random.

Input Sanitation

One of the most significant security vulnerabilities web developers are always fighting is a SQL injection attack. In this attack, users of a website format input so that their information gets interpreted as code in the web developers’ systems. The most straightforward mechanism for preventing such an attack is to remove the offending characters before they get used in inappropriate ways.

Details

Write the Python function sanitize(text: str) -> str that sanitizes text by removing all non-alphabetic characters. The parameter text is a string containing any text. The function should return a copy of text with all characters that are not letters removed.

Test Cases

import test

def sanitize(text: str) -> str:
    # Put your code here

def main() -> None:
    test.equal(sanitize("Hello, World!"), "HelloWorld")
    # Put more test cases here
    return None

main()

Hint

Challenge

In the real world, the true offending characters are double and single quotes. Write a new function called escape_quotes(text) that returns a copy of text with all single or double quotes "escaped". Recall that a quote can be escaped in a string by pre-pending it with a backslash (\" or \').

Pig Latin Translator

Pig Latin is a somewhat silly language parody that is actually entirely English based. It is a simple transposition of letters that gives the effect of a "foreign" sounding language. The rules for converting an English word to Pig Latin are incredibly easy:

• If the first character of the word is a vowel, append the string "yay" to the end.

• If the first character is a consonant, then all consonants up to (but not including) the first vowel are moved to the end. A ' character is placed between the transposed characters. Then the string "ay" is appended to the word.

Details

Write the Python function to_pig_latin(text: str) -> str that converts English to Pig Latin. The parameter text is a string containing text in English. The function should return text converted to Pig Latin as a string.

Test Cases

import test

def to_pig_latin(text: str) -> str:
    # Put yourcode here

def main() -> None:
    test.equal(to_pig_latin("scram"), "am'scray")
    # Put more test cases here return None
    return None

main()

Hint

Challenge