Python: Python Setup & First Program

Q: When should I use the interactive interpreter vs a .py file?

Use the interactive interpreter ( >>> prompt) for quick experiments — testing a single line, checking a function's behavior, or exploring a new module. Use .py files for anything you want to save, reuse, or share. A good rule: if it's more than 3 lines, put it in a file.

Q: My Python file runs but the window closes instantly. How do I see the output?

This happens when you double-click a .py file on Windows — the terminal opens, runs the code, and closes. Solutions: ① Open the terminal first, then run python myfile.py ; ② Add input("Press Enter to exit...") at the end of your script; ③ Run from VS Code's built-in terminal instead of double-clicking.

Before diving into Python syntax, let's get your development environment ready. All you need is Python installed and a text editor.

1. Installing Python

(1) Windows

Go to https://python.org and click Downloads
Download the latest Python version (e.g., 3.13.x)
Run the installer — make sure to check "Add Python to PATH"
Open Command Prompt (cmd) and verify with python --version

TEXT 📖 Display only

C:\Users\YourName> python --version
Python 3.13.2

(2) Mac

Mac comes with Python 2 (too old), so you need to install Python 3:

Go to https://python.org and download the Mac installer
Run the installer, or use Homebrew: brew install python3
Verify in the terminal: python3 --version

(3) Linux

Most Linux distributions already have Python 3 installed:

BASH

# Ubuntu/Debian
sudo apt install python3

# Verify
python3 --version

2. Hello World Program

Once installed, your first program is always "Hello, World!".

(1) Method 1: Interactive Interpreter

Type python (Windows) or python3 (Mac/Linux) in your terminal to enter interactive mode:

TEXT 📖 Display only

Python 3.13.2 (main, Feb  4 2025, 14:51:09)
Type "help", "copyright", "credits" or "license" for more information.
>>> print("Hello, World!")
Hello, World!
>>> 1 + 2
3
>>> exit()

💡 The interactive interpreter is great for quickly testing code snippets, but not ideal for writing complete programs.

(2) Method 2: Create a .py File

Create a new file called hello.py
Enter this code:

PYTHON

print("Hello, World!")

Run it from the terminal:

BASH

python hello.py

Output:

TEXT 📖 Display only

Hello, World!

3. Choosing an Editor

You don't need a complex IDE when you're just starting out. Here are some recommendations:

Editor	Best For	Pros
VS Code	Beginners (recommended)	Free, lots of extensions, lightweight
PyCharm	Professional development	Most features, great autocomplete
IDLE	Absolute beginners	Comes with Python, ready out of the box
Jupyter Notebook	Data analysis	Run code in cells, great for interactive learning

💡 We recommend VS Code with the Python extension — lightweight and powerful.

(1) VS Code Setup

Download and install VS Code (code.visualstudio.com)
Open VS Code, press Ctrl+Shift+X to open the Extensions panel
Search for "Python" and install Microsoft's official Python extension
Create a new file and save it with a .py extension
Right-click in the editor → "Run Python File in Terminal"

▶ Example: Interactive Greeting Program (Difficulty ⭐)

Let's put it all together and write a small interactive program:

PYTHON

# First Python program
name = input("What's your name? ")
print("Hello, " + name + "! Welcome to Python!")

▶ Try it Yourself

When you run it:

TEXT 📖 Display only

What's your name? Alice
Hello, Alice! Welcome to Python!

▶ Example: Your First Calculation Program (Difficulty ⭐)

PYTHON

# Simple calculations in Python
name = "Python Learner"
birth_year = 2000
current_year = 2026

age = current_year - birth_year
print(f"Hello, {name}!")
print(f"You are approximately {age} years old.")
print(f"Fun fact: you've lived about {age * 365} days!")

▶ Try it Yourself

Output:

TEXT 📖 Display only

Hello, Python Learner!
You are approximately 26 years old.
Fun fact: you've lived about 9490 days!

▶ Example: Self-Introduction with Variables (Difficulty ⭐)

PYTHON

# Build a self-introduction using variables and f-strings
name = "Alice"
age = 25
hobby = "programming"
experience = 2

print("=" * 30)
print("     Self Introduction")
print("=" * 30)
print(f"Name:     {name}")
print(f"Age:      {age}")
print(f"Hobby:    {hobby}")
print(f"Experience: {experience} year(s)")
print(f"Fun:      I've written approximately {experience * 50} programs!")
print("=" * 30)

▶ Try it Yourself

Output:

TEXT 📖 Display only

==============================
     Self Introduction
==============================
Name:     Alice
Age:      25
Hobby:    programming
Experience: 2 year(s)
Fun:      I've written approximately 100 programs!
==============================

4. Common Pitfalls

PATH not set (Windows): You MUST check "Add Python to PATH" during installation, otherwise the terminal won't find the python command
python vs python3: Windows uses python, Mac/Linux use python3
Chinese encoding issues: Python 3 uses UTF-8 by default, so garbled text is rare. If you do run into encoding issues, add # -*- coding: utf-8 -*- at the top of your file

❓ FAQ

Q What's the difference between an IDE, a text editor, and Python itself?

A Python is the language runtime — it executes your code. A text editor (Notepad, VS Code) is where you write code. An IDE (PyCharm, VS Code with extensions) bundles an editor with debugging, autocomplete, and other tools. For beginners, VS Code strikes the best balance — lightweight like an editor, extensible like an IDE.

Q I typedpythonbut got 'python is not recognized'. What went wrong?

A This is the #1 beginner issue — Python isn't on your system PATH. When you type a command in the terminal, the OS looks for it in a list of directories called PATH. Fix: reinstall Python and make sure to check "Add Python to PATH." Or manually add C:\Python3xx\and C:\Python3xx\Scripts\to your system environment variables.

Q When should I use the interactive interpreter vs a .py file?

A Use the interactive interpreter (>>> prompt) for quick experiments — testing a single line, checking a function's behavior, or exploring a new module. Use .py files for anything you want to save, reuse, or share. A good rule: if it's more than 3 lines, put it in a file.

Q My Python file runs but the window closes instantly. How do I see the output?

A This happens when you double-click a .py file on Windows — the terminal opens, runs the code, and closes. Solutions: ① Open the terminal first, then run python myfile.py; ② Add input("Press Enter to exit...") at the end of your script; ③ Run from VS Code's built-in terminal instead of double-clicking.

📖 Summary

Download and install Python 3.x from python.org
On Windows, check "Add Python to PATH" during installation
Interactive interpreter: type python in the terminal
.py files: write code in an editor, run with python filename.py
VS Code + Python extension is the recommended development setup

📝 Exercises

Install Python and type python --version in the terminal — take a screenshot
Write a hello.py file that prints "Hello, World!" and run it successfully
In the interactive interpreter, calculate (5 + 3) * 2 and 10 / 3 — observe the results
Modify the interactive program above by adding an age variable, and print "Your name is XX, you are XX years old"

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About Us

Python: Python Setup & First Program

1. Installing Python

(1) Windows

(2) Mac

(3) Linux

2. Hello World Program

(1) Method 1: Interactive Interpreter

(2) Method 2: Create a .py File

3. Choosing an Editor

(1) VS Code Setup

▶ Example: Interactive Greeting Program (Difficulty ⭐)

▶ Example: Your First Calculation Program (Difficulty ⭐)

▶ Example: Self-Introduction with Variables (Difficulty ⭐)

4. Common Pitfalls

❓ FAQ

📖 Summary

📝 Exercises

🙏 帮我们做得更好