P ython p rogramming e xercises

Solution Template 
Try to first write a solution from scratch. But if you have difficulty, you can use the following 
partial program as a starting place. Copy the following code from https://invpy.com/rot13-template.py and 
paste it into your code editor. Replace the underscores with code to make a working program: 
def rot13(text): 
# Create an encryptedText variable to store the encrypted string: 
encryptedText = ____ 
# Loop over each character in the text: 
for character in text: 
# If the character is not a letter, add it as-is to encryptedText: 
if not character.____(): 
encryptedText += ____ 
# Otherwise calculate the letter's "rotated 13" letter: 
else: 
rotatedLetterOrdinal = ____(character) + 13 
# If adding 13 pushes the letter past Z, subtract 26: 
if ____.islower() and rotatedLetterOrdinal > ____: 
rotatedLetterOrdinal -= ____ 
if ____.isupper() and rotatedLetterOrdinal > ____: 
rotatedLetterOrdinal -= ____ 
# Add the encrypted letter to encryptedText: 
encryptedText += ____(rotatedLetterOrdinal) 
# Return the encrypted text: 
return encryptedText 
The complete solution for this exercise is given in Appendix A and https://invpy.com/rot13.py. You 
can view each step of this program as it runs under a debugger at https://invpy.com/rot13-debug/. 
Further Reading 
If you are interested in writing Python programs for encryption algorithms and code breaking, 
my book ―Cracking Codes with Python‖ is freely available under a Creative Commons license at 
https://inventwithpython.com/cracking/.

---

130 
E X E R C I S E # 4 2 : B U B B L E S O R T
bubbleSort([2, 0, 4, 1, 3])
→ 
[0, 1, 2, 3, 4] 
Bubble sort is often the first sorting algorithm taught to computer science students. While it is 
too inefficient for use in real-world software, the algorithm is easy to understand. In this last exercise 
of the book, we’ll implement this basic sorting algorithm.