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Python Shebang: How to Effortlessly Specify the Interpreter

Executing Python Scripts With a Shebang

When you come across Python code, you may have noticed a line at the top of the file that starts with #! called a shebang. This line may seem like a comment, but it serves a special purpose. In this tutorial, we will explore what a shebang is, when to use it, and how to use it correctly.

What’s a Shebang, and When Should You Use It?

In short, a shebang is a special kind of comment that you can include in your Python code to specify the interpreter the operating system’s shell should use to execute the rest of the file. This is particularly useful when you have multiple versions of Python installed on your system.

To use a shebang, you need to add it as the first line of your script and start it with #!. Following the shebang, you should provide the absolute path to the relevant code interpreter, such as #! for Python 3.

It’s important to note that shebangs are recognized by shells on Unix-like operating systems, including macOS and Linux distributions. They are not recognized by the Windows terminal, which treats the shebang as a regular comment.

To make shebangs work on Windows, you can either install the Windows Subsystem for Linux (WSL), which comes with a Unix shell, or create a file association between a file extension like .py and the Python interpreter.

How Does a Shebang Work?

When you include a shebang in your code, it tells the shell which program should be used to execute the code. For example, if you include #! as the shebang, the shell will use the Python 3 interpreter to run the code.

The shebang acts as a directive to the shell, allowing you to specify which interpreter and version to use. This is useful when you have scripts that require a specific Python version or use other programming languages.

How Can You Define a Portable Shebang?

To create a portable shebang that can be used across different systems, it’s recommended to use as the interpreter path instead of specifying an absolute path to a specific Python executable. This allows the system to search for the interpreter in the user’s PATH environment variable.

To define a portable shebang, you can use the following syntax:

#! python3

This shebang tells the shell to use the python3 interpreter found in the user’s PATH. This ensures that the script can be executed regardless of the specific location of the Python interpreter on different systems.

What Are Shebang Examples?

Here are some examples of common shebangs:

  • #! This shebang specifies the Python 3 interpreter located at
  • #! python3: This shebang uses the env command to search for the python3 interpreter in the user’s PATH.
  • #! python: This shebang searches for the python interpreter in the user’s PATH and uses the first one found.

By using a portable shebang, you can ensure that your script can be executed on different systems without requiring the user to modify the shebang to match their specific Python installation.

How Can You Use a Shebang With a Custom Interpreter in Python?

In addition to using the default Python interpreter, you can also use a shebang to specify a custom interpreter for your script. This can be useful when you want to use a different Python implementation or a specific version of Python.

For example, if you have a custom Python interpreter installed at, you can use the following shebang to execute your script with that interpreter:


This allows you to run your script with a custom Python environment without modifying the system-wide Python installation.

What Are Best Practices for the Shebang?

When using a shebang in your Python scripts, there are a few best practices to keep in mind:

  1. Use a portable shebang: By using python3 or a similar portable shebang, you can ensure that your script can be executed on different systems without modification.
  2. Choose the right interpreter version: Make sure to specify the correct version of Python that your script requires. Using python3 instead of python can help prevent compatibility issues between Python 2 and Python 3.
  3. Include required dependencies: If your script depends on external libraries or modules, make sure to include the necessary import statements or installation instructions in your script or documentation.

By following these best practices, you can create Python scripts that are easy to run and maintain on different systems.


In this tutorial, we explored the concept of a shebang and learned how to use it correctly in Python scripts. We discussed when to use a shebang, how to define a portable shebang, and how to use a custom interpreter. We also covered some best practices for using shebangs in your Python code.

By utilizing shebangs effectively, you can ensure that your Python scripts can be executed with the desired interpreter and version, making them more portable and versatile.