Running Python from the Command Line

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Before You Begin

This guide assumes you have:

Python installed on your computer (check our installation guide if needed)
Basic familiarity with the terminal (see our terminal basics guide)

Two Ways to Use Python

There are two main ways to use Python from the command line:

Interactive Mode: Type Python code directly and see results immediately
Script Mode: Run Python programs saved in .py files

Interactive Mode (Python Shell)

Starting the Python Shell

Open your terminal and type:

Windows: python
Mac/Linux: python3

You should see something like this:

Python 3.13.1 (main, Jun 7 2023, 00:00:00)
[GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

Or, on Windows, you'll probably see:

Python 3.13.1 (tags/v3.13.1:0671451, Dec  3 2024, 19:06:28) [MSC v.1942 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

The >>> prompt means Python is ready for your commands!

Using the Python Shell

Try these commands:

>>> print("Hello, World!")
Hello, World!

>>> 2 + 2
4

>>> name = "Coder"
>>> print(f"Hello, {name}!")
Hello, Coder!

Exiting the Python Shell

To exit the Python shell, type:

>>> exit()

Or press Ctrl+D (Mac/Linux) or Ctrl+Z then Enter (Windows)

Script Mode (Running .py Files)

Running a Python File

To run a Python file, navigate to its folder in the terminal, then:

Windows: python filename.py
Mac/Linux: python3 filename.py

Example: Running Your First Script

Create a file called greet.py with this content:

name = input("What's your name? ")
print(f"Nice to meet you, {name}!")
print("Welcome to Python programming!")

Save the file
In the terminal, navigate to the file's location
Run it:
- Windows: python greet.py
- Mac/Linux: python3 greet.py

Common Python Commands

Check Python Version

python --version

Or on Mac/Linux:

python3 --version

Run a Script with Arguments

You can pass information to your Python script:

python script.py argument1 argument2

Get Help

python --help

Troubleshooting Common Issues

"Python is not recognized"

This means Python isn't in your system's PATH. Try:

Reinstalling Python and checking "Add to PATH" during installation
Using the full path to Python (like C:\Python311\python.exe)
Check our installation guide for help

"No such file or directory"

This means Python can't find your file. Make sure:

You're in the correct folder (use cd to navigate)
The filename is spelled correctly (including .py extension)
Use dir (Windows) or ls (Mac/Linux) to see files in current folder

SyntaxError

This means there's a mistake in your Python code. Check for:

Missing colons (:) after if statements, loops, or function definitions
Incorrect indentation (Python uses spaces to organize code)
Unclosed quotes or parentheses

Practice Exercises

Exercise 1: Calculator in Interactive Mode

Open the Python shell and try these calculations:

>>> 15 + 7
>>> 100 - 33
>>> 12 * 8
>>> 50 / 5
>>> 2 ** 10  # This means 2 to the power of 10

Exercise 2: Create and Run a Script

Create a file called calculator.py

Add this code:

print("Simple Calculator")
num1 = float(input("Enter first number: "))
num2 = float(input("Enter second number: "))

print(f"{num1} + {num2} = {num1 + num2}")
print(f"{num1} - {num2} = {num1 - num2}")
print(f"{num1} * {num2} = {num1 * num2}")
print(f"{num1} / {num2} = {num1 / num2}")

Run the script from your terminal

Tips for Command Line Python

Use the up arrow: Recall previous commands in both the terminal and Python shell
Tab completion: Press Tab to autocomplete file names
Copy and paste: Right-click in most terminals to paste code
Clear screen: In Python shell, press Ctrl+L to clear the screen

What's Next?

Now that you can run Python from the command line, try:

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