Welcome to CS Room

Welcome to CS Room

In this lesson you'll use the terminal, write a Python program, save data to a file, and put a web page on the internet at an address anyone can open.

Work through the five parts in order. Each part starts by opening a terminal in the right folder, so you can pick up where you left off on another day.

Part 1: Find your way around

CS Room has three panels:

• The file list (left): your folders and files. Click a file to open it, right-click for more options.
• The editor (middle): where you read and write code. Changes save on their own.
• The terminal (bottom): where you type commands and run programs.

Right-click this lesson's folder in the file list and choose Open in terminal. Then type this in the terminal and press Enter:

pwd

pwd means "print working directory". It shows the folder the terminal is in.

Part 2: Terminal basics

Three keys save a lot of typing:

• Tab finishes a file or folder name for you. Type cd pa and press Tab.
• Up arrow brings back your last command.
• Ctrl+C stops a running program. It doesn't copy in the terminal; to copy, select the text and press Ctrl+Shift+C (or Cmd+C on a Mac).

Try them out:

mkdir practice
cd practice
touch song.txt movie.txt
ls
cd ..
rm -r practice

Watch the file list on the left as you go. The terminal and the file list show the same files.

Part 3: Your first program

Right-click the part3 folder and choose Open in terminal. Open part3/hello.py. It's one line:

print("Hello, world!")

Run it:

python hello.py

Now change the file so it asks for your name:

name = input("What's your name? ")
print(f"Hello, {name}!")

Run it again with python hello.py (press the up arrow to get the command back). The green Run button above the editor also runs the file you have open.

If you have time: change hello.py so it asks for a number and prints its times table:

What number? 7
7 x 1 = 7
7 x 2 = 14
...
7 x 10 = 70

You'll need int(input(...)) to turn what the user types into a number, and a for i in range(1, 11): loop.

Part 4: Save to a file

Programs remember things between runs by writing files.

Right-click the part4 folder and choose Open in terminal. (From the terminal, cd ../part4 does the same thing if you're still in part3: .. means "the folder above".) Then:

python journal.py

Type write and then a journal entry. Run ls and you'll see a new file, journal.txt. Print it with cat journal.txt.

If you have time: run python journal.py again and type read. Nothing happens, because read_journal() isn't written yet. Open journal.py, find the TODO, and finish it. Test it by writing a few entries and reading them back.

Part 5: Put a page on the internet

Right-click the part5 folder and choose Open in terminal. Then:

pip install -r requirements.txt
python app.py

The first command installs Flask, the library that runs the web server. When the server starts, a message pops up saying the port is live, with a web address and an Open button. Click Open to see your page.

If you miss the message, click Ports next to the terminal tabs to find the address again.

That address works on any device. Send it to a classmate.

Leave the server running and open app.py. Change the text inside <h1>...</h1>, then refresh the page in your browser. The server restarts on its own when the file changes.

Press Ctrl+C in the terminal to stop the server. The address stops working until you start it again.