I am using "Learn Python the Hard Way" and using PyScripter for writing and running my code.
On Exercise 13 I have to make the following code run:
from sys import argv
script, first, second, third = argv
print "The script is called:", script
print "Your first variable is:", first
print "Your second variable is:", second
print "Your third variable is:", third
When I run it, I get an error saying
ValueError: need more than 1 value to unpack
I have read other questions about the same topic and can't seem to find an answer that works.
I am also quite new to coding so explaining how to do it would be great!
Your script will only work if you pass exactly three commandline arguments to it. For example:
script.py 1 2 3
You cannot use any other number of commandline arguments or else a ValueError will be raised.
Perhaps you should make your script a little more robust by checking how many arguments you received and then assigning the names first, second, and third appropriately.
Below is a demonstration:
from sys import argv, exit
argc = len(argv) # Get the number of commandline arguments
if argc == 4:
# There were 3 commandline arguments
script, first, second, third = argv
elif argc == 3:
# There were only 2 commandline arguments
script, first, second = argv
third = '3rd'
elif argc == 2:
# There was only 1 commandline argument
script, first = argv
second = '2nd'
third = '3rd'
elif argc == 1:
# There was no commandline arguments
script = argv[0]
first = '1st'
second = '2nd'
third = '3rd'
else:
print "Too many commandline arguments"
exit(1)
print "The script is called:", script
print "Your first variable is:", first
print "Your second variable is:", second
print "Your third variable is:", third
Of course, this is just an example. You can do anything you want inside the if-statements (assign the names to something different, raise an exception, print a message, exit the script, etc.). The important part here is the argc = len(argv) line and the if-statements which check how many arguments the script received.