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How to Run Python Code: Interactive Prompt, IDLE, and Command Line

Learn how to run Python code with the interactive prompt, IDLE, and saved .py files from Windows Command Prompt or a Linux shell.

After installing Python, you can run code in several beginner-friendly ways. The three most common are the interactive Python prompt, IDLE, and command-line execution of a saved script.

How Python code is executed

The Python interpreter is the program that reads and executes Python code. You can give it code interactively, open code through IDLE, or ask it to execute a saved file.

A script is a saved file containing Python instructions. Python source files normally use the .py extension, such as example.py.

The command line is a text-based terminal interface. On Windows, this is commonly Command Prompt. On Linux, it is commonly a shell such as Bash. The command used to start Python can vary by operating system and installation.

Run code in the interactive Python prompt

The interactive prompt is a command-line Python session. It is also called a REPL, which means Read-Eval-Print Loop: Python reads what you enter, evaluates it, prints a result when appropriate, and waits for more input.

1. Open a terminal

• Windows: Open Command Prompt from the Start menu.
• Linux: Open your terminal application.

2. Start the interpreter

Try the command appropriate for your installation:

python

On many Linux systems, Python 3 is started explicitly:

python3

On Windows installations that provide the Python launcher, you can use:

py

A successful launch displays information about Python followed by a prompt that commonly looks like >>>.

3. Enter an expression

At the prompt, enter an expression and press Enter:

>>> 2 + 2
4

You can also enter a statement such as:

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

The result appears immediately, which makes the REPL useful for trying syntax, checking calculations, and exploring Python features.

4. Leave the interactive session

Use one of these options:

• Enter exit() and press Enter.
• Enter quit() and press Enter.
• On Windows, press Ctrl+Z, then Enter.
• On Linux, press Ctrl+D.

After leaving Python, you return to the normal operating-system command prompt or shell.

Use IDLE to edit and run Python code

IDLE is Python's basic integrated development environment. It includes a Python shell for immediate commands and an editor for source files. IDLE is typically installed with Python, although some installation choices or distributions may omit it.

Open IDLE

• Windows: Search the Start menu for IDLE, such as “IDLE (Python 3.x).”
• Linux: Open it from the application menu if it was installed, or start it from a terminal with an available IDLE command.

The IDLE Shell window works like the interactive prompt. Enter a command after >>> to see its result immediately.

Create and run a file in IDLE

1. Open IDLE.
2. Choose the option to create a new file in the editor.
3. Enter a short program:

print("Hello, Python!")

4. Save the file with a .py extension, for example example.py.
5. Run the saved module using IDLE's Run command, commonly available from the Run menu.
6. Read the output in the IDLE Shell window.

IDLE provides basic editing features, syntax highlighting, and beginner-level debugging support. It is useful when you want a graphical workflow without installing a larger development environment.

Run a saved Python file from the command line

When Python is started by itself, it opens an interactive session. When a filename follows the interpreter command, Python executes that file instead.

First create a file named example.py containing:

print("Hello, Python!")

Then open Command Prompt or a Linux shell and run the file:

python example.py

Depending on your system, the equivalent commands may be:

python3 example.py
py example.py

The command has two parts: the interpreter command starts Python, and example.py tells it which saved program to execute.

Run a script from its folder

The terminal has a working directory, meaning the current folder in which commands are being run. If the script is in that folder, its filename is enough:

python example.py

If the script is elsewhere, change to its folder first:

cd path-to-script-folder
python example.py

You can also provide a relative or absolute path directly:

python path-to-script-folder/example.py

On Windows, a path may use a drive letter and backslashes:

python C:\path\to\example.py

Python commands and the PATH environment variable

The PATH environment variable is a system setting containing directories that a terminal searches when you enter a command. If the directory containing the Python interpreter is in PATH, commands such as python can be found from any working directory.

If the terminal says that Python is “not recognized,” “not found,” or cannot be located, common causes include:

• Python is not installed.
• The Python installation directory is not in PATH.
• Your system uses a different command, such as python3 or py.
• Several Python installations exist and the command points to another one.

Try the available launch commands

Check which command works and verify its version:

python --version
python3 --version
py --version

Run only the command that is available on your system. The output should identify the installed Python version.

Use the full interpreter path

One solution is to provide the complete filesystem path to the interpreter. This does not depend on PATH:

"C:\path\to\python.exe" example.py

On Linux, the equivalent form is:

/full/path/to/python3 example.py

This is useful for testing a specific installation or working around an incorrectly configured PATH.

Add Python to PATH

Another solution is to add the directory containing the Python executable to the system PATH. After changing PATH, open a new terminal and run a version check such as:

python --version

Adding Python to PATH makes the interpreter easier to launch, but multiple installations can make command selection confusing. Verify the version before running an important program.

Troubleshoot common problems

Python cannot be found

Try python3 on Linux or py on Windows. If neither works, check whether Python is installed, use its full path, or add its installation directory to PATH.

The script cannot be opened

An error such as “no such file” usually means the terminal is in the wrong working directory, the filename is incorrect, or the path was omitted. Use cd, check the exact spelling and .py extension, or provide the complete path.

cd path-to-script-folder
python example.py

The wrong Python version starts

Multiple Python installations may exist, or PATH may list one installation before another. Check the reported version and use python3, py, a version-specific launcher option if available, or an explicit interpreter path.

IDLE is unavailable

Search the installed applications for IDLE. If it is missing, modify or reinstall Python with the IDLE component included. Until then, you can use the interactive prompt or command-line script execution.

Which method should you choose?

• Choose the interactive prompt for a quick calculation or a small experiment.
• Choose IDLE when you want a simple graphical editor, shell, and basic debugging tools.
• Choose command-line script execution when your code is saved and you want to run it repeatedly or as part of a terminal workflow.

For more practice, return to running Python code and try each method with the same example.py program.