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Computer Programming with Scratch
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Python and VS Code Setup

Python and VS Code Setup

Everything in the Python unit starts here. Do this once, then come back when something breaks.

Is Python Installed?

  1. Press cmd + space to open Spotlight.
  2. Type IDLE and press return.
  3. IDLE opens: Python is installed. Click next to the >>> prompt, type print("Hello, world!"), and press return. You should see Hello, world! on the next line.
  4. Nothing comes up: Python is not installed. Continue below.

Installing Python

  1. Press cmd + space, search for Self Service, and open the CCSD Self Service app.
  2. Search for Python and click Install. Wait for it to finish.
  3. Search Spotlight for IDLE again. It should open now.
If Self Service is not working or Python will not install, raise your hand before going any further.

Opening VS Code

  1. Press cmd + space, type Visual Studio Code, and press return.
  2. Go to File → Open Folder….
  3. Choose your Desktop, click New Folder, name it python-class, and click Open.

Every Python file you write this unit goes in python-class. If VS Code asks whether you trust the authors of the folder, click Yes.

Writing and Running a Script

  1. File → New File, then File → Save as hello.py inside python-class. The .py ending matters.
  2. Type:
print("Hello, world!")
print("Python is working.")
  1. Save with cmd + S.
  2. Click the Run (play) button in the top-right corner of the editor. The output appears in the terminal panel at the bottom.

You can also run a script from the integrated terminal (Terminal → New Terminal, or ctrl + `):

python3 hello.py

Basic Terminal Commands

CommandWhat it doesExample
lsList the files and folders where you arels
pwdPrint the full path of where you arepwd
cdMove into a foldercd Desktop
cd ..Go up one foldercd ..
mkdirMake a new foldermkdir my-project
touchMake a new, empty filetouch notes.txt
python3 file.pyRun a Python scriptpython3 hello.py

Installing Libraries

A library is code someone else wrote that you can use. Install from the VS Code terminal, once per library:

python3 -m pip install pandas matplotlib

The terminal scrolls for a while. When the prompt comes back, it is done. If pip prints an error, raise your hand.

Troubleshooting

python3: command not found Python is not installed. Install it from Self Service (above), then quit and reopen VS Code.

The Run button runs the wrong file The Run button runs whichever file is open in the editor. Click into the file you want first.

My file runs but nothing appears A script with no print() runs silently. That is normal. Add a print().

SyntaxError Python found a typo. The message gives a line number; go there and look for a missing colon, a mismatched quote, or a misspelled word.

FileNotFoundError when reading a CSV The data file is not in the same folder as the script. Drag it into python-class and run again.

A plot window will not close, or windows keep piling up Close each plot window before running the script again.

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