How to check if the parameter exist in python

Question

I would like to create a simple python script that will take a parameter from the console, and it will display this parameter. If there will be no parameter then I would like to display error message, but custom message not something like IndexError: list index out of range

Something like this:

if isset(sys.argv[1]):
    print sys.argv[1];
else:
    print "No parameter has been included"

Answer 1

if len(sys.argv) >= 2:
    print(sys.argv[1])
else:
    print("No parameter has been included")

For more complex command line interfaces there is the argparse module in Python's standard library - but for simple projects taking just a couple parameters directly checking sys.argv is alright.

update as of 2019, the recomendation is to use the external library "click", as it provides very "Pythonic" ways of including complex documents in a way they are easily documented.