ValueError: not enough value to unpack

Question

hi

1 from says import argv
2
3 script, first, second, third = argv
4
5 print("the script is called:", script)
6 print("your first variable is:", first)
7 print("your second variable is:", second)
8 print("your third variable is:", third)

when I run it I get this:

... line 3, in <module>
...script, first, second, third = argv
ValueError: not enough values to unpack ( expected 4, got 1)

Answer 1

argv is an arguments vector (list) containing arguments passed when running a program from command line

if you would simply do print(argv) you will see a file name.
that's because the first argument is always the program's name

in your example, as i suspect the progarm did not ran from command line, so there weren't any additional arguments passed on

look at the example in the following link:

https://www.daniweb.com/programming/software-development/threads/401173/interpret-from-sys-import-argv-into-english-please

from that page, in the example:
~~~~~~
from sys import argv
print(argv[0])
print(argv[1])
print(argv[2])
print(argv[3])

command line call:
test.py david 8 jenny

output:
>>> test.py
david
8
jenny
~~~~~~~

if you were to run the same script you supplied, there would be no issues, as the command line call supplies 3 additional arguments, making it a total of 4

TL;DR

argv is an argument list and in your example it did not have enough arguments, which caused the error as the program tried to unpack a list with 1 element into 4 seperate objects