1 Better than C++ and Java

The first time that you work with command line arguments in Python… one might write…

import sys


def main():
    for idx in range(1, len(sys.argv)):
        print(f"Argument #{idx:>3} was {sys.argv[idx]}")


if __name__ == "__main__":
    main()

Note that idx is my usual loop counter. It is short for “index.” I prefer to reserve i for mathematical code.

Similar to C++… sys.argv[0] is the program itself.

#include <iostream>
#include <iomanip>

using namespace std;


int main(const int argc, const char* const* argv)
{
    for (int idx = 1; idx < argc; ++idx) {
        cout << "Argument #" 
             << right << setw(3) << idx
             << " was "
             << argv[idx]
             << '\n';
    }
}

However, if you are familiar with Java… you are used to args[0] as the first user supplied argument.

public class CLIDemo
{
    public static void main(String[] args)
    {
        for (int idx = 1; idx < args.length; ++idx) {
            System.out.printf("Argument %3d was %s%n", idx, args[idx])
        }
    }
}

2 That is Not Quite Pythonic

However, Python for loops are usually for-each (a.k.a range based), not index based. Let us try rewriting the loop

import sys


def main():
    for idx, arg in enumerate(sys.argv):
        print(f"Argument #{idx:>3} was {arg}")


if __name__ == "__main__":
    main()

But… that is not quite right! We want to skip argv[0].

import sys


def main():
    for idx, arg in enumerate(sys.argv[1:], start=1):
        print(f"Argument #{idx:>3} was {arg}")


if __name__ == "__main__":
    main()

3 Wait… “for” is not Count Based?