This question already has answers here:
Python Value Error: not enough values to unpack
(4 answers)
Closed 2 years ago.
I'm using Learning Python the Hard Way. In the process of my learning I came across this error. Though I have been trying to debug since yesterday, I couldn't.
This is my code:
import sys
from sys import argv
script, first, second = argv
print('the script is called:', script)
print('the first variable is:', first)
print('the second vriable is:', second)
print('the third variable is:', third)
The error you're getting means you're trying to deconstruct an iterable (list, tuple) into more values than there are in the actual list. If you were to run
print(argv, len(argv))
You might see that you don't have three variables in argv.
argv shows the parameters you provided while running a script. So for example, if I ran:
python test_args.py
I would only receive: ['test_args.py'] as my argv variable. If I tried providing more parameters, like:
python test_args.py a b
Then my argv would look like: ['test_args.py', 'a', 'b']. Your code is completely dependent on how many parameters are passed when you are running it, so mess around with that as well to get a better sense of what is going on.
I suppose that you are executing the script in this format
python script.py 10 20
The problem is that you are using an extra variable third which is not initialized.
If you really want 3 arguments, then you have to pass three values at execution time as follows.
python script.py 10 20 30
Then change the code as follows.
from sys import argv
script, first, second, third = argv
print('the script is called:', script)
print('the first variable is:', first)
print('the second vriable is:', second)
print('the third variable is:', third)
Thank you
Related
I'm trying to learn python by following book Named "learn python3 by hard way"
They gave this example of code.
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)
But in VS code pylint giving me this error.
Possible unbalanced tuple unpacking with sequence: left side has 4 label(s), right side has 0 value(s)
Book writer hadn't explained this and I want to know what does this error means
But they also said
Run the program like this (and you must pass three command line
arguments):
$ python3.6 ex13.py first 2nd 3rd
And how often python programmers use this method in practical world and any example of use-case.
The argument may not exactly be four. If it is less or more than 4, it may raise ValueError
I am getting valueError in this code.
I do not know why?
from sys import argv
(script,first,second,third)=argv
print('The script is called:',script)
print('The first variable is :',first)
print('The second variable is :',second)
print('The third variable is :',third)
You're either not providing enough arguments to run your script or providing too many arguments, you need to provide three arguments like this:
python3 script.py first second third
I'm practicing Python with the book called Learn "Python The Hard Way 3rd edition". I searched that this book is a good resource to get a start.
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)
And I got an error saying that value error: not enough values to unpack (expected 4, got 1).
You need to run the script with three arguments, so that argv contains four elements (the first is the script's name).
argv is a list containing the following:
argv[0] is the script pathname if known
argv[1], argv[2], argv[3]... contains arguments passed from the shell.
In order for your code to work you need to run it with 3 arguments so that they can be unpacked and assigned to your 4 variables.
Please help.
I am doing this exercise, but I am using jupiter to do the exercise. This is written for python 2
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 virable is:", third)
How do I write it correctecly in Python 3 . Thanks a lot!
This same example works in Python 3 as well.
```
>> python unpack.py 4 5 3
The script is called: unpack.py
Your first variable is 4
Your second variable is: 5
Your third virable is: 3
```
You can specify the arguments in such a way:
python arg1 arg2 ...
Same would work for Python3 as well, you don't need to change anything. But as a safe practice, do check for the arguments length. You don't want to crash your script. Good luck.
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
How can I pass command-line arguments in IronPython?
I am new to ironpython and sharpdevelop and I am trying to run the following code,
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
How do I pass the arguments to the command line ?
In SharpDevelop you
right-click on the python project
choose Properties in the context-menu
choose the Debug-tab
append your arguments in the Command line arguments field
Does this article help you at all?
You need to set the values of sys.argv.
engine.Sys.argv = List.Make(args);