How to Pass and Unpack Command‑Line Arguments in Python

In Python, a script can receive values from the command line, which are essential for making programs flexible without hard‑coding data. After the previous lesson on list operations, we now focus on how arguments are passed and unpacked.

First, the script must import the sys module, which provides access to interpreter variables, including argv. The import statement is explicit so that only required functionality is loaded, keeping the code lightweight and making dependencies clear to other developers. from sys import argv When the script runs, argv is automatically populated with a list where the first element is the script name and the subsequent elements are the arguments supplied on the command line. By assigning this list to a variable—commonly named script —the programmer effectively “unpacks” all arguments into a single, easy‑to‑handle container.

script = argv
print(script)

Running the file with a command such as python first.py a b c produces the output: ['first.py', 'a', 'b', 'c'] This demonstrates that the arguments a, b, and c have been collected into a list and assigned to script, which is then printed. The list format allows the programmer to apply any of the list manipulation techniques covered in the previous chapter, such as indexing, slicing, or iteration.

The accompanying screenshot (shown below) captures the command‑line execution and the resulting list output, reinforcing the concept that command‑line parameters are automatically converted into a Python list.

By understanding this import‑and‑unpack pattern, developers can write scripts that accept arbitrary numbers of arguments, process them using familiar list operations, and thus build more reusable and interactive command‑line tools.