Python, as a versatile and widely-used programming language, offers several ways to execute code. One of the most common and practical methods is to write code in a text file, save it with a .py extension, and then run it using Python’s interpreter. This approach allows for the organization of code into manageable modules, facilitates code reuse, and enables the development of more complex and scalable applications. In this article, we will discuss in detail how to execute Python code from files, including the basics of creating and running .py scripts, handling errors, and using Python’s interactive mode for debugging and testing.
Creating a Python Script
To execute Python code from a file, you first need to create a text file with a .py extension. This file is commonly referred to as a “script” or a “Python script.” Inside this file, you can write your Python code just as you would in Python’s interactive mode.
Here’s a simple example of a Python script named hello.py:
python# hello.py
print("Hello, world!")
Running a Python Script
Once you have created your Python script, you can run it by invoking Python’s interpreter and passing the script file as an argument. How you do this depends on your operating system and how Python is installed on your machine.
On most Unix-like systems (including macOS), you can open a terminal and type the following command:
bashpython3 hello.py
Note that some systems might require you to use python instead of python3 if Python 3 is the default version installed.
On Windows, you can open a Command Prompt or PowerShell window and type:
cmdpython hello.py
If Python is not recognized as a command in your system’s PATH, you may need to specify the full path to the Python interpreter executable.
Handling Errors
When executing Python scripts, it’s important to be aware of potential errors. Python will display an error message if it encounters a syntax error or a runtime error while executing the script. These error messages can be invaluable for debugging and fixing issues in your code.
Using Python’s Interactive Mode for Debugging and Testing
While executing Python code from files is the standard approach for developing applications, Python’s interactive mode can be a useful tool for debugging and testing code snippets. In interactive mode, you can type Python code directly into the interpreter and see the results immediately. This can be particularly helpful when you’re troubleshooting a specific part of your script or trying out a new idea.
To enter Python’s interactive mode, simply open a terminal or command prompt and type python (or python3 on Unix-like systems). Once you’re in interactive mode, you can type your Python code and press Enter to execute it. To exit interactive mode, you can type exit() or use the keyboard shortcut Ctrl+D (on Unix-like systems) or Ctrl+Z followed by Enter (on Windows).
Conclusion
Executing Python code from files is a fundamental aspect of Python programming. By organizing your code into .py scripts, you can create modular, reusable, and scalable applications. In this article, we’ve covered the basics of creating and running Python scripts, handling errors, and using Python’s interactive mode for debugging and testing. With these skills in hand, you’re well-equipped to start writing and executing your own Python programs.
Python official website: https://www.python.org/
