The error is at script, first, second, third = argv. I would like to understand why I am getting the error and how to fix it.
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)
Run it from the shell like this:
python script.py arg1 arg2 arg3
argv variable contains command line arguments. In your code you expected 4 arguments, but got only 1 (first argument always script name). You could configure arguments in pycharm. Go to Run -> Edit Configurations. Then create a new python configuration. And there you could specify Script parameters field. Or you could run your script from command line as mentioned by dnit13.
You could run it like this: python script.py first, second, third
I think you are running the following command:
python script.py
You are writing a program which is aksing for 4 inputs and you are giving onle one. That's why you are receiving an error. You can use the below command:
python script.py Hello How Are
Related
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 am new in python.I am doing addition of two numbers in cmd using input parameter .I am getting output on cmd but getting Error on python shell.I am using windows 7 and python shell 3.3.2 . so anyone can tell me why my code is not running on python shell ?
code:
import sys
n=int(sys.argv[1])
m=int(sys.argv[2])
print(n+m)
Error:
Traceback (most recent call last):
File "C:/pythonprogram/add.py", line 4, in
n=int(sys.argv[1])
IndexError: list index out of range
Your program is expecting two command line arguments.
sys.argv is a list of command line arguments. The error IndexError: list index out of range is telling you that you tried to get list item number 2, (with index 1), but the list doesn't have that many values.
You can reproduce that error in the shell:
>> alist = ['Item 0']
>> print(alist[1])
Since alist only has item with index 0 requesting items with higher indexes will cause that error.
Now, to your exact problem. The program is telling you it expected command line arguments, but they were not provided. Provide them!
Run this command:
python add.py 1 2
This will execute the script and pass 1 as the first argument, 2 as the second argument.
In your case the general format is
python add.py [n] [m]
Now at that point you might be (you should be) wondering what sys.argv[0] is then, any why your n number doesn't get assigned to sys.argv[1].
sys.argv[0] is the name of the script running.
Further reading on command line arguments:
http://www.pythonforbeginners.com/system/python-sys-argv
Additional.
You could modify your script to be more descriptive:
import sys
if len(sys.argv) < 3: #script name + 2 other arguments required
print("Provide at least two numbers")
else:
n=int(sys.argv[1])
m=int(sys.argv[2])
print(n+m)
sys.argv contains the command line parameters. When you run your script in the Python shell you're most likely not sending any parameters. I would suggest adding a check if there are command line arguments present like this:
import sys
if len(sys.argv) > 2:
n=int(sys.argv[1])
m=int(sys.argv[2])
print(n+m)
Check this out to find out more about Python and sys.argv
I wrote the following command but I don't understand it.
from sys import argv
what is argv?
how to use it?
I wrote sycript,a,b=argv
but I am getting the error that need more than one value to unpack.
argv - The list of command line arguments passed to a Python script.
sycript,a,b=argv gives you "ValueError: need more than 1 value to unpack" because you have just run the script as python <script_name.py> without giving the two arguments.
Run the script like this: python <script_name.py> <arg1> <arg2>
For example,
script.py:
from sys import argv
arg,a,b=argv
print(arg,a,b)
run script.py "arg1" "arg2" and output:
script.py arg1 arg2
I think you should run the command by typing
python scriptname a b
By scriptname I mean the name by which you have saved the program code.
I hope this helps..
I'm running the code below in Spyder.
I have typed it in a py file and simply hit the run button.
When I try to run it I get the error:
ValueError: need more than 1 value to unpack
As shown here you are meant to give the inputs for the argv variable before running the program but I don't know how to do this is spyder?
http://learnpythonthehardway.org/book/ex13.html
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 "Your third variable is:", third
To pass argv to a script in Spyder, you need to go the menu entry
Run > Configuration per file
or press the Ctrl+F6 key, then look for the option called
Command line options
on the dialog that appears after that, and finally enter the command line arguments you want to pass to the script, which in this case could be
one two three
In addition to configuring in the Run->Configure as explained in other answers,
you can use "runfile" directly from the console.
Run the following:
runfile('ex13.py', args='first second third')
In Spyder, go Run > Configure and define your argv values as showing in following diagram and to run the script just press F6
Read the FAQ at the bottom of the page, it specifically mentions this error.
Common Student Questions
Q. When I run it I get ValueError: need more than 1 value to unpack.
Remember that an important skill is paying attention to details. If you look at the What You Should See section you see that I run the script with parameters on the command line. You should replicate how I ran it exactly.
Make sure you run the command:
$ python ex13.py first 2nd 3rd
>> The script is called: ex13.py
>> Your first variable is: first
>> Your second variable is: 2nd
>> Your third variable is: 3rd
You can ensure that the arguments are supplied.
if __name__ == '__main__':
if len(argv) == 4:
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
else:
print 'You forgot the args...'
First off I looked in the documentation and found this:
http://www.tutorialspoint.com/python/python_command_line_arguments.htm
And then I also found this:
how to execute a python script file with an argument from inside another python script file
I am using pycharm 2.7.3 and when I try to run my script I get and error (the error is not pycharm related). THe only way around this error I have found out to be is to run the script through the windows PowerShell with a couple of "arguments" (is that what its called?)
The code that follows is what makes up my script, temp.py
from sys import argv
# this what the Ide fails to run
scripts, first, second, third = argv
print "The script is called:", scripts
print "Your first variable is:", first
print "Your second variable is:", second
print "Your third variable is:", third
Next is what I types into the powershell
NOTE: The above code is temp.py
python temp.py first 2nd 3rd
1) What are those pieces of text called that appear after the "python temp.py", is it arguments?
2) Is it possible to run the code with the so called arguments in the IDE (I am using pyCharm)
3) If '2)' = True, how so?
1) What are those pieces of text called that appear after the "python temp.py", is it arguments?
Yes, the things you pass after temp.py on the shell are called "arguments", or "command line arguments". Sometimes they're called "parameters" instead, sometimes with the word "actual" as a prefix.*
And note that temp.py and all of its arguments are themselves arguments of python.
The sys.argv variable that you're using specifically gives you:
The list of command line arguments passed to a Python script…
2) Is it possible to run the code with the so called arguments in the IDE (I am using pyCharm)
Yes. Almost every IDE has a way to do this.
3) If '2)' = True, how so?
Read the PyCharm docs for details, but IIRC, they're part of the "run/debug configuration"; when you use the "Edit Configurations" command and edit one, there's a box labeled "Script Parameters" for you to enter the arguments.
* Using "parameters" is a bit misleading. Speaking technically, using the terminology Python uses for function calling, you should say that your script has a single parameter, a variable-positional parameter which gathers all of the arguments used to call it, which you can access as sys.argv. But as you can guess, nobody actually says things that way. If someone says "command line parameters" or "script parameters", they mean "the things in sys.argv".