Creating and Running Python Scripts in VS Code

Hello. In the previous lesson, you learned to establish your location with pwd, inspect folders with ls, and move through paths with cd. You will use exactly those skills now to make a small, real Python project folder.

By the end of this lesson, you will be able to create a Python file in VS Code, edit its contents, save it, and run it from a terminal. This is the basic development loop behind every later automation: change the program, run it, inspect what happened, then change it again.

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The three tools that work together

A Python script is a plain-text file containing Python instructions. Its filename ends in .py, such as hello_agent.py.

Three separate tools collaborate:

1. VS Code is where you create and edit the file.
2. The Python extension in VS Code adds Python-aware features, including syntax coloring and convenient Run commands.
3. The Python interpreter is the program that actually reads and executes your .py file.

VS Code does not itself “understand” how to execute Python without an interpreter. The extension helps VS Code locate and use that interpreter.

Readiness check

Open the macOS Terminal app and run:

python3 --version

A successful result looks broadly like this:

Python 3.x.x

The exact version number is not important yet. What matters is that the command begins with Python 3.

Next, open VS Code and check the Extensions view in the left sidebar. Search for Python and ensure the extension is installed from the publisher Microsoft.

If python3 is not found and you already have Homebrew installed, the Microsoft guide’s macOS command is:

brew install python3

After installing Python, close and reopen Terminal before repeating:

python3 --version

Your M1 MacBook Air has more than enough capacity for VS Code and ordinary Python scripts. Later, when working with language models, you will be more deliberate about memory use; for now, this setup is lightweight.

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Create a project folder from Terminal

Rather than scattering scripts around the Desktop, keep them in a project folder. This small organizational habit pays off when a project eventually contains data files, configuration, tests, and documentation.

In Terminal, enter these commands one at a time:

cd ~
mkdir -p agent_builder/first_script
cd agent_builder/first_script
pwd

You should see a path similar to:

/Users/your-short-username/agent_builder/first_script

Here is what the unfamiliar command did:

• mkdir means “make directory.”
• -p permits Terminal to create the missing parent folders, agent_builder and first_script, in one command.
• Running the same command again is safe: it does not erase or overwrite existing files.
• cd moved you into the folder where this first script will live.

Confirm that it is currently empty:

ls

No output is normal for a new, empty directory.

Open the folder as a VS Code workspace

A workspace is the folder VS Code has opened as the home for a project. Opening a folder rather than a random untitled file helps VS Code, the terminal, and you agree on where the project lives.

Use either method:

• In VS Code, choose File > Open Folder..., then select agent_builder/first_script in your home folder.
• Or, if the code command has already been configured on your Mac, run this from the first_script folder:

code .

The dot means “the current directory,” exactly as in the navigation lesson. If code . reports that the command is not found, simply use File > Open Folder.... Nothing is wrong with Python.

Once the folder is open, look at VS Code’s Explorer panel on the left. It should show the folder name first_script.

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Create and edit your first script

In the Explorer panel, select the New File icon. Name the file:

hello_agent.py

The .py ending is important. It tells VS Code that the file contains Python, so it can enable Python-specific support.

Type this code into the editor:

print("Hello from my first Python script.")
print("I am learning to build dependable automations.")

Then save it with Command-S.

For now, read each print(...) line as an instruction that tells Python to display the text between the quotation marks. We will examine text, variables, and Python data types carefully in the next lessons; this lesson is about the edit-and-run workflow.

Before running anything, check the Python interpreter selection in VS Code:

1. Look at the bottom status bar, usually toward the right.
2. If you see a Python version, VS Code has selected an interpreter.
3. If it says Select Interpreter, click it and choose the current Python 3 installation.

A selected interpreter makes VS Code’s Run command predictable. You can always bypass the VS Code button and call python3 yourself in a terminal, but having both point to the same interpreter avoids confusion.

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Run the script in the integrated terminal

Open VS Code’s integrated terminal through Terminal > New Terminal. A panel appears at the bottom of VS Code. This is a normal shell terminal, just embedded inside the editor.

First, verify that it opened in the project folder:

pwd
ls

You should see the path ending in agent_builder/first_script and a listing containing:

hello_agent.py

Now run your script explicitly:

python3 hello_agent.py

The terminal should print:

Hello from my first Python script.
I am learning to build dependable automations.

This command has two parts:

Part	Meaning
python3	Start the Python 3 interpreter.
hello_agent.py	Give Python the file it should execute.

The terminal output is not being written into your script. It is the result of Python executing the instructions in the saved file.

This explicit command is worth learning even though VS Code offers buttons. It works in Terminal, VS Code’s integrated terminal, and later in automated workflows.

Make one edit, save, and run again

Add a third line to hello_agent.py:

print("Each run starts again at the top of the file.")

Save with Command-S, then run the same terminal command again:

python3 hello_agent.py

You should now see all three messages. Python runs a script from top to bottom each time you execute it. The earlier terminal output does not mean the file has “kept running”; it is simply the record of the previous run.

This is the essential loop:

1. Edit the saved .py file in VS Code.
2. Save the file.
3. Run the file with python3 filename.py.
4. Read the terminal output.
5. Make the next deliberate change.

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Use VS Code’s Python Run command

VS Code can issue the terminal command for you. With hello_agent.py open, look for the Run Python File play button near the top-right of the editor.

You can also right-click inside the editor and choose the command named something like:

Run Python > Run Python File in Terminal

The exact menu wording can vary slightly across VS Code versions, but it will include Python File in Terminal.

When you use this command, VS Code opens or reuses an integrated terminal and runs a command equivalent to:

python3 hello_agent.py

The button is convenient, but it is not a different kind of execution. It is still Python executing a saved file in a terminal.

For the next few lessons, prefer either the explicit terminal command:

python3 hello_agent.py

or Run Python File in Terminal. Both execute the whole saved program, which reduces surprises.

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Resolve common first-run problems

Problems at this stage are usually setup or path issues, not evidence that you are “bad at programming.” Diagnose the message literally and check one layer at a time.

zsh: command not found: python3

Terminal cannot find a Python 3 interpreter. Re-run:

python3 --version

If it still fails, complete the Python installation step, then close and reopen Terminal. A newly opened terminal reads the latest system configuration.

can't open file 'hello_agent.py'

Python is installed, but Terminal is not currently in the folder containing your file. Check:

pwd
ls

If hello_agent.py is not listed, return to the project folder:

cd ~/agent_builder/first_script

Then run:

python3 hello_agent.py

This is a direct use of relative and home-directory paths from the previous lesson.

VS Code has no Python Run button

Check these three things:

1. The file is saved with the exact .py extension.
2. The Microsoft Python extension is installed and enabled.
3. A Python interpreter is selected in the VS Code status bar.

Even while you solve the VS Code configuration, you can still run the script manually from Terminal with python3 hello_agent.py.

You edit the file but see the old output

Save before running. In VS Code, Command-S is the deliberate way to ensure that what you see in the editor is what Python reads from disk.

The output text differs from the lesson

That is fine if you intentionally changed the text. Python prints exactly the characters inside your quotation marks. Check for a missing quotation mark, parenthesis, or a typo in print if the terminal displays an error instead.

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What you should now be able to do

You have achieved this outcome when you can independently:

• Navigate to ~/agent_builder/first_script in Terminal.
• Open that folder in VS Code as a workspace.
• Create a file ending in .py.
• Type and save a small Python script.
• Verify that python3 --version works.
• Run the script with python3 hello_agent.py.
• Run the same script with VS Code’s Run Python File in Terminal command.
• Edit one line, save, rerun, and identify the changed output.

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You now have a working Python development loop: Terminal locates and runs the program, VS Code is where you edit it, and the Python interpreter executes it. Keep the agent_builder/first_script folder; it is the beginning of an organized set of hands-on projects.

Next, you will make scripts store and work with information by using Python variables and the basic types for text, numbers, and true-or-false values.