PYTHON· LESSON 01

Python Setup

Install Python, set up your development environment, and run your first Python program.

This guide helps you install Python, run a first program, create a virtual environment, and install packages.

You can write Python in VS Code, Notepad, or any other text editor. The editor does not run Python. The terminal runs Python.

Contents

Windows

Follow this article by GeeksForGeeks:

https://www.geeksforgeeks.org/python/how-to-install-python-on-windows/

Run a First Program

Open Notepad and save this as hello.py:

print("Hello from OSDC")

When saving in Notepad:

  • Set Save as type to All files.
  • Save the file as hello.py, not hello.py.txt.

Open a terminal in the folder containing the file. In File Explorer, open the folder, click the address bar, type powershell, and press Enter.

Run the program:

python hello.py

If this command doesn’t work, you might’ve forgotten to add Python to PATH. So, try the following steps.

Add Python to PATH Manually

Use this only if running the python.org installer again with Add python.exe to PATH does not fix the problem. If you installed Python from the Microsoft Store and python --version works, Python is already available and you do not need this section.

Find the installation without using a Python command: open the Start menu, search for Python, right-click the Python result, and choose Open file location. If this opens a shortcut, right-click the shortcut and choose Open file location again. The folder containing python.exe is the folder you need.

For a python.org installation, its Scripts folder is usually next to the folder containing python.exe. Add both folders to PATH. If you cannot find Python, run the python.org installer again and select Add python.exe to PATH.

To edit PATH:

  1. Search Windows for environment variables.
  2. Open Edit the system environment variables.
  3. Select Environment Variables.
  4. Under User variables, select Path and choose Edit.
  5. Add both folders with New.
  6. Confirm all dialogs.
  7. Open a new terminal and run python --version again.

macOS

Follow this article by GeeksForGeeks:

https://www.geeksforgeeks.org/python/how-to-install-python-on-mac

Run a First Program

Create a file named hello.py in any editor:

print("Hello from OSDC")

Open Terminal in that file’s folder and run:

python3 hello.py

Using Any Editor

VS Code, Notepad, Notepad++, nvim, vim, nano, emacs and other editors can be used to write Python files.

Code::Blocks is not recommended for Python because it is primarily designed for C and C++, but it can still be used as an editor.

The basic workflow is always:

  1. Create a plain-text file ending in .py.
  2. Write Python code.
  3. Save the file.
  4. Open a terminal in the file’s folder.
  5. Run the file with Python.

VS Code

  1. Install VS Code from:

    https://code.visualstudio.com/

  2. Install the official Python extension by Microsoft.

  3. Open your project folder.

  4. Open a .py file.

  5. Select the Python interpreter if VS Code asks.

  6. Open the integrated terminal with Terminal > New Terminal.

  7. Run the file from the terminal:

    python filename.py

On macOS and Linux, use python3 filename.py before activating a virtual environment.

VS Code also provides a Run Python File button in the top-right of a Python file. It uses the interpreter selected in VS Code.

Notepad

Notepad is enough for the first Python programs. Save the file with the .py extension and make sure it does not become .py.txt.

Virtual Environments

A virtual environment is a separate Python setup for one project. Packages installed inside it stay separate from other projects.

Create the environment inside your project folder.

Windows PowerShell

python -m venv .venv
.venv\Scripts\Activate.ps1

Windows Command Prompt

python -m venv .venv
.venv\Scripts\activate.bat

macOS and Linux

python3 -m venv .venv
source .venv/bin/activate

After activation, the terminal usually begins with (.venv). Check that the environment is active:

python --version
python -m pip --version

On Windows, use the same commands after activation.

Installing Packages

Activate the virtual environment first, then install the package with Python’s pip module.

python -m pip install requests

For the FastAPI workshop:

python -m pip install "fastapi[standard]"

Install packages listed in an existing project file:

python -m pip install -r requirements.txt

Using python -m pip makes sure the package is installed for the Python interpreter currently being used.

Deactivating the Environment

When you are finished working, run:

deactivate

You can activate the same .venv again the next time you work on the project.

Troubleshooting

python Is Not Recognized on Windows

If you installed Python from python.org, you can optionally check whether its launcher is available:

py --version

The py command may not exist, especially when Python was installed from the Microsoft Store. If py is also not recognized, reinstall Python from python.org with Add python.exe to PATH enabled. You can then run programs with python filename.py.

Python Opens the Microsoft Store

Turn off the python.exe and python3.exe entries in Windows App execution aliases, then reopen the terminal.

PowerShell Does Not Allow Activation

Run this command as your normal user:

Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy Unrestricted

Then try activation again.

The File Is Called .py.txt

Enable File name extensions in File Explorer and rename the file so it ends exactly in .py.

A Package Cannot Be Imported

Make sure the virtual environment is active, then install the package again:

python -m pip install package-name