Week 3 · Session 1

Comments, Markdown, and Strings

Lab 1 questions & the parts of a repository that are not Python.

Four Errors You Have Probably Hit

Read the last line of the error first. It names the problem.

ValueError: invalid literal for int(): you gave int() something that is not a number, often a piece with a stray space in it
TypeError: can only concatenate str (not "int") to str: you joined a number onto a string. Convert first
ValueError: not enough values to unpack: the left side of mm, dd, yyyy = ... wants exactly three pieces and got a different number
KeyError: 0: get_anchor_day received a month of 0, so a placeholder above it was never replaced

Questions to Ask Your Own Program

Run through these in order before you ask anyone for help.

Does print(mm, dd, yyyy) show three pieces that look right
By the next line, are month, day and full_year integers, or still strings
For the year 2026, does century hold 20 and decade hold 26
Does the last line print exactly 11-25-2026: Wednesday, colon and one space included

Try It: Splitting a Year

Fix the two lines so they print 20 26.

Both operators you need take 100. One keeps what division throws away
Then change the year to 1999 and confirm you get 19 99

full_year = 2026
century = full_year        # want 20
decade = full_year         # want 26
print(century, decade)

Session 1

Comments

Lines Python ignores, written for the humans reading your code.

# starts a comment. Everything after it on that line is skipped when the program runs
The # TODO: lines in main.py are comments. They are instructions to you, not code
A comment can sit on its own line, or trail one: decade = full_year % 100 # 2026 becomes 26
Two spaces before a trailing #. That is the spacing Python programmers expect to see

Comment the Why, Not the What

# add one to count above count = count + 1 says nothing the code did not already say
# a leap year adds an extra day explains something the code cannot say for itself
The triple-quoted block at the top of main.py is a docstring. Put your name on its Author: line
Delete each # TODO: once you have done it. A file still full of them reads as unfinished
A comment that is wrong is worse than no comment. Update it when you change the line under it

Try It: Comments

Run it. Fix line 3. Then comment out line 2 and add a line of your own.

Nothing prints at all, not even line 2. Python checks the whole file before it runs any of it
Line 3 is the problem: its trailing text is not marked as a comment yet
The error names the line number. Start there every time

# print("this line does not run")
print("this line does")
temperature = 72  this text is not a comment yet

Session 1

Markdown

The other file you edited in lab: docs/summary.md.

A .md file is plain text plus a few punctuation marks that mean formatting
GitHub renders it for you. That is why a README looks like a document on the repository page and like symbols in the editor
The four questions waiting in docs/summary.md are written in markdown too
Nothing is hidden. The characters you type are the entire format

The Whole Syntax You Need

Click Preview to see what this becomes. Then click Write and change it.

Add a third bullet, and make one word in it bold
A blank line is what separates one paragraph from the next. Take one out and preview again

# A Heading

## A Smaller Heading

Plain text is a paragraph. Put **bold** around a word with two stars, and *italic* with one.

Wrap `code` in backticks so it does not read as ordinary prose.

- a bullet
- another bullet

1. a numbered item
2. the next one

> A blockquote, which is how each question in your lab summary is marked.

Your Lab Summary Is Markdown

Replace the first TODO with a real two-sentence answer, then Preview.

Each question is a > blockquote, and the word TODO under it is the placeholder
Delete the marker itself. Answer in full sentences, not fragments
Preview before you push, so you catch a heading that did not render

# Lab Summary

> Which part of this lab took you the longest, and why?

TODO

> What would you do differently if you started it again?

TODO

Previewing Markdown for Real

The box on the last two slides is a demonstration. Here is where you do it.

In VS Code, open the .md file and press Cmd+Shift+V on a Mac, Ctrl+Shift+V on Windows
Or click the split-pane preview icon at the top right of the editor to get both at once
On GitHub, every .md file is already rendered when you view it in the browser
Markdown joins consecutive lines into one paragraph. A blank line is what actually breaks them apart

Week 3 · Session 2

Working With Strings

Joining them, repeating them, and converting into and out of them.

Session 2

Joining Strings With +

"Good" + "bye" gives "Goodbye". No space appears unless you put one there yourself
first + " " + last is how two names become "Ada Lovelace"
+ between two numbers adds. + between two strings joins. Same symbol, and the types decide which job it does
"Room " + 101 is an error. "Room " + str(101) gives "Room 101"

Try It: Joining

Run it first. Line 3 prints but is wrong, and line 6 crashes.

Fix line 3 so a space lands between the two names
Fix line 6 by converting room with str()

first = "Ada"
last = "Lovelace"
print(first + last)          # want Ada Lovelace

room = 101
print("Room " + room)        # want Room 101

Session 2

Repeating Strings With *

"ha" * 3 gives "hahaha". A string times a whole number repeats it
"=" * 50 gives a line of fifty equals signs, which is how a banner line gets printed
That is one number to change when you want a longer line. Typing fifty equals signs is not
"ha" * "3" is an error. The count has to be an int, not a string

Try It: Repeating

Run it, fix the last line, then change every 10 to 24 and run it again.

The last line fails for the same reason "Room " + 101 did, in the other direction
Then add a line that prints your own name three times with a space after each copy

print("=" * 10)
print("Results")
print("=" * 10)

print("-" * "20")            # want a line of 20 dashes

Session 2

Three Ways to Print the Same Thing

All three are correct Python. They differ in how much you have to track yourself.

print("Total:", total): commas, and Python puts a space between each piece for you
print("Total: " + str(total)): joining, so every character is yours, including that space
print(f"Total: {total}"): an f-string, which converts for you and keeps the text readable
You will read all three in other people’s code. Write whichever makes the line clearest

Your Turn: One Line, Three Ways

Fill in all three so each prints: notebook costs 3 dollars

The comma version is the one to watch. Check exactly where the spaces land
Only one of the three needs str(). Work out which, and why

item = "notebook"
price = 3
# each line should print: notebook costs 3 dollars
print()     # use commas
print()     # use + and str()
print()     # use an f-string

Session 2

Converting Between Types

int("26") gives 26. str(26) gives "26". float("3.5") gives 3.5
int("3.5") is an error. Go through float first: int(float("3.5")) gives 3
input() always hands back a string, so a number the user typed always needs converting
len("Lovelace") gives 8, the number of characters, and that is an int you can do arithmetic on

Before Lab

Lab 1 Is Due at 2:30 Today

Run uv run gatorgrade --config gatorgrade.yml from the top folder of your repository, not from inside src
Finish docs/summary.md. It is graded, it is markdown, and it takes one preview to check
git add ., then git commit -m "message", then git push. Nothing counts until it is on GitHub
Your code review happens in lab this afternoon. Arrive with the project open and pushed

In Lab Today

Activity 2: The Calculation Report

Code reviews first. Then this, and it uses everything from the last two weeks.

Two whole numbers go in, and a formatted report of every operation we have covered comes out
You choose how the two numbers are separated, and your prompt has to say so
The sum with commas, the difference with + and str(), the product with an f-string. Same text, three ways, on purpose
Build the report line with repetition. Nobody types 34 equals signs