Understanding sys.argv: How to Properly Pass Command Line Arguments in Python

Discover the correct way to utilize `sys.argv` in Python to pass command line arguments, ensuring your scripts receive the input you intend. --- This video is based on the question https://stackoverflow.com/q/65014215/ asked by the user 'Sean' ( https://stackoverflow.com/u/14702255/ ) and on the answer https://stackoverflow.com/a/65014617/ provided by the user 'Mustafa Quraish' ( https://stackoverflow.com/u/13782556/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Using sys.argv to pass command line arguments to a python script Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l... The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- Understanding sys.argv: How to Properly Pass Command Line Arguments in Python Command line arguments enable us to provide additional data to scripts when executing them. However, many users encounter issues with using sys.argv to capture these arguments effectively in Python. In this post, we’ll explore a common problem one might face with sys.argv and how to overcome it. Let’s dig into the details! The Problem Imagine you have a simple Python script, test.py, which you expect to run and print a "Hello world!" message along with the command line arguments you pass to it. Here’s your script: [[See Video to Reveal this Text or Code Snippet]] When you try executing your script from the command line like this: [[See Video to Reveal this Text or Code Snippet]] You receive the following output: [[See Video to Reveal this Text or Code Snippet]] As you can see, the two expected arguments (test and test) are absent from the output. The issue arises from the way Windows handles script execution through the command line. The Solution: Running the Script Correctly Using the Python Interpreter Directly To ensure your script receives the intended arguments, you need to invoke it through the Python interpreter explicitly. Instead of just running the script with: [[See Video to Reveal this Text or Code Snippet]] You should run it as follows: [[See Video to Reveal this Text or Code Snippet]] Why Does This Work? When you run test.py test test directly from the command line, Windows interprets it differently. It looks for a file or a command to execute with the name test.py and assumes that the additional words (the two test arguments) might be filenames or commands, not arguments. Since the first entry (test.py) is recognized as a Python script due to its .py extension, it is executed, but the subsequent words aren’t passed as parameters. Here’s the breakdown: No Interpreter Invocation: Without prefixing it with the Python interpreter, Windows may not pass the additional parameters correctly to the script. Direct Execution of File: When attempting to run just test.py, the other words may be viewed as file paths or commands. Using a Batch File to Pass Arguments Another approach that worked for you was creating a batch file. Your batch file (test.bat) looked like this: [[See Video to Reveal this Text or Code Snippet]] When you executed: [[See Video to Reveal this Text or Code Snippet]] You received the desired output: [[See Video to Reveal this Text or Code Snippet]] What Does %* Do? The %* in the batch file allows all arguments entered after the batch file name to be passed along to the Python script. Thus, this approach successfully captures all intended command-line arguments. Conclusion To summarize, when passing command-line arguments to Python scripts on Windows, ensure that you either run the script directly using the Python interpreter or use a batch file that forwards the arguments correctly. Whether you opt for direct invocation or a batch file, understanding how to manage command line arguments using sys.argv is essential for effective script execution. If you encounter issues or unexpected output when running your Python scripts this way, remember to check how you’re calling them and consider using the methods discussed. Happy coding!