"list index out of range" when using sys.argv[1]

Question

I am writing a simple Python client and server, which works fine passing the server address within my code, however, I want the user to be able to enter the server address and throw and error if its incorrect. When I have the code below I get a error message from the terminal "list index out of range".

server = (sys.argv[1])
serverAdd = (server, '65652') # server address and port number

Can anyone help me with this please.

When I run my client program in python I want to be able to enter a address to connect to and store that in server. I run the program directly from the command line by typing programname.py. The server is already running listening for incoming connections.

You may want to try printing the list to make sure there's something there. `print(sys.argv)` — , Feb 27 '13 at 20:35
"enter the server address": As a parameter on the commandline or on stdin? — Sebastian, Feb 27 '13 at 20:41
"is the above not a command line call": I don't see a commandline call, here. Please show how you called the server program. — Sebastian, Feb 27 '13 at 20:42
"is the above not a command line call?" Not unless by "the above", you mean the "I run the program directly from the command line by typing programname.py" part. The problem is that you should write something **after** `programname.py`, in order to tell the program what the value for `server` should be. — Karl Knechtel, Aug 09 '22 at 08:23

Jason Sperske · Accepted Answer · 2013-02-27T20:50:15.430

17

With this Python:

import sys

print(sys.argv)

And invoked with this command:

>python q15121717.py 127.0.0.1

I get this output:

['q15121717.py', '127.0.0.1']

I think you are not passing a argument to your Python script

Now you can change your code slightly to take a server form the command line or prompt for a server when none is passed. In this case you would look at something like this:

if len(sys.argv) > 1:
    print(sys.argv[1])
else:
    print(input("Enter address:"))

edited Feb 27 '13 at 20:50

answered Feb 27 '13 at 20:44

Jason Sperske

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I think your right. I am i write in thinking that sys.argv[1] would be the second element etc...... so in the case above sys.argv['127.0.0.1'] – user1978826 Feb 27 '13 at 20:49

"list index out of range" when using sys.argv[1]

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