I'm trying to use 'argv' into my python script. For this i'm using following code:

from sys import argv
script, file_name = argv
print(file_name)

python3 e.py e.txt This code works fine.

But when I use:

import sys

and try to use 'argv', I get error:

'NameError: name 'argv' is not defined '.

I don't understand this as by importing 'sys' full module becomes usable into my code.

Can you explain why does this happen? How to packages work?

Thank you.

Import sys does not give you direct access to any of the names inside sys itself To access those you need to prefix them with sys:

sys.argv
sys.exit()

If you want use argv instead sys.argv try

from sys import *