What is “argv”, and what does it do?

Question

argv

What on Earth is it!?

Edit: If you can, will you please write a line or two and explain how it works?

Answer 1

sys .argv will display the command line args passed when running a script or you can say sys.argv will store the command line arguments passed in python while running from terminal

It stores the arguments in a list ds.

sample usage: Create a file say: cmdlineargs.py and put the following in it:

import sys
print sys.argv 

Now run the file in your terminal/cli :

python cmdlineargs.py 

or something like

python cmdlineargs.py example example1

Notice what happens now. Your script will print everything passed in your cmd line argument while you ran that script.

Important to know:

print len(sys.argv) #total arguments passed
sys.argv[0] #this is your script name stored in sys.argv.
print sys.argv #display all arguments passed
sys.argv[0] #is the first argument passed, which is basically the filename.
sys.argv #stores all cmd line args in a list ds

You can look up each specific argument passed like this, probably:

cmdLineArg = len(sys.argv)
i=0
for argv in sys.argv:
    if cmdLineArg<=len(sys.argv) :
        print "argument",i,"is", str(sys.argv[i])
        i=i+1
    else:
        print "Only script name in sys.argv"

Sample result:

Say you run the following in your terminal.

python cmdlineargs.py example example1

Your result should look something like:

argument 0 is cmdlineargs.py
argument 1 is example
argument 2 is example1  

Notice argument 0 is the same as the file name . Hope this was helpful.

---

Thanks for the upvotes, improving my answer for the loop. A little more pythonian answer should look like this:

i=0
for argv in sys.argv:
    if cmdLineArg==1:
        print "Only script name in sys.argv"
    elif (cmdLineArg>1 and cmdLineArg<=len(sys.argv)):
        print "argument ",i,"is", str(argv)
        i=i+1
print "total arguments passed:\t", totalargs

I too am new to python so I had a habit of declaring i and j for traversing arrays. :)