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
basically, does script here mean the file of the programm? like ex14.py?
im complete new to python and prgramming...if this question sound stupid to you all.
Running it with the arguments: 1 2 3
Output:
The script is called: E:\Proyectos\Eclipse\Python\Test\__init__.py
Your first variable is: 1
Your second variable is: 2
Your third variable is: 3
The first line prints the script name. Quoting Python Docs:
... argv[0] is the script name (it is operating system dependent whether this is a full pathname or not).
The following 3 lines just prints the arguments I passed 1 2 3.
Related
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...'
I was reading "Learn Python 3 the Hard Way" and was testing the 'from sys import argv' there is an error occuring here is the sample code of the book:
from sys import argv
first, second, third = argv
print("The scipt is called:", script)
print("Your first variable is:", first)
print("Your second variable is:,", second)
print("Your third variable is:", third)
An I got this error:
Traceback (most recent call last):
File "d:/MyCodes/PythonCodes/jon.py", line 2, in
first, second, third = argv
ValueError: not enough values to unpack (expected 3, got 1)
Argv will be an array with your commandline arguments this is trying to split the list into, first, second, third.
Use argn to know how many arguments to expect
from sys import argn, argv
for i in range(argn):
print(f”arg {i}: {argv[i]}”)
argv returns list of prarameter passed in command line
argv[0] = script name
argv[1] = first value passed in to program, and so on.
from sys import argv
script,first, second, third = argv
print("The scipt is called:", script)
print("Your first variable is:", first)
print("Your second variable is:,", second)
print("Your third variable is:", third)
For this script your command should look like this
python filename.py firstval secondval thirdval
for Variable lengthn arguments you can use argn as mentioned in one of the answer
from sys import argv
# read the WYSS section for how to run this
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)
In WWSS section(What You Should See) in first line you see what you should enter in
PowerShell. Line goes like this:
$ python3.6 ex13.py first 2nd 3rd
First thing:
You wrote your code wrong on line two: look mine to see where you have mistaken,
You are missing script variable.
Second:
What you probably entered in terminal is this:
$ python3.6 ex13.py
Notice how you should enter 3 variables that are missing.
Argv are named before running the script in the same line as the script name.
Hope this helped you!
For the following Python script named ex13.py:
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)
I have a question about the following line of code:
script, first, second, third = argv
We are saying assign argv to four variables on the left in this order.
Then when I, use this script in my terminal:
python ex13.py first 2nd 3rd
I understand that we are passing variables to a script using the terminal as an input method. However what's confusing me is this.
When I was writing basic Python scripts the way I would call them is with:
python ex3.py
Am I correct in saying that this python ex3.py is not passing a single command line argument and python ex13.py first 2nd 3rd is passing several?
When working from the command line, argv returns a list of the command line arguments, where the first (at place zero argv[0] we get the python file name that was used after the pyhton name).
from place one and up, the values are related to the order in which arguments was recieved. take note that if you use optional arguments (python myscript.py -p 127.0.0.1) those are counted in argv too. so you will get argv[1] == -p
Am I correct in saying that this python ex3.py is not passing a single
command line argument and python ex13.py first 2nd 3rd is passing
several?
no, you are incorrect, python ex3.py is passing 1 argument, argv[0] = ex3.py.
Hi I am new to programming and pycharm. I want to run the code below through the python console. I need to enter 3 values to run it. I tried python p13.py one two three but it didn't work.
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
Could you help me with what am I meant to type into the python consle in pycharm in order to run this.
I'm reading "Learn Python the Hard Way" and I'm on exercise 13, but I'm running into a little trouble. Whenever I open up the command line and run the script and enter my argument variables, it's always duplicated on every line like this:
C:\users\blah\> program.py first second third
The script is called:['program.py','first','second','third']
Your first variable is:['program.py','first','second','third']
Your second variable is:['program.py','first','second','third']
Your third variable is:['program.py','first','second','third']
So instead of seeing this on every line I'm aiming for something that doesn't duplicate every line like this (without brackets):
C:\users\blah\> program.py first second third
The script is called:'program.py'
Your first variable is:'first'
Your second variable is:'second'
Your third variable is:'third'
This is my original code. Note I'm on Python 3.5, even though it's specified to use 2.7.
from sys import argv
script = argv
first = argv
second = argv
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)
Pretty sure the whole variable part is off.
The code in the example is:
from sys import argv
script, first, second, third = argv
When you execute your script with program.py first second third argv becomes a list containing the name of your script followed by each of the scripts arguments. So argv becomes this:
argv = ['program.py', 'first', 'second', 'third']
The line in the original code 'unpacks' the members of that list and assigns them to individual variables. It is equivalent to:
script = argv[0]
first = argv[1]
second = argv[2]
third = argv[3]
It is simply a more concise way of expressing the above. This unpacking syntax is one of the things Zed Shaw is trying to teach with that example. When you changed the program to:
script = argv
first = argv
second = argv
third = argv
the 'unpacking' went away - each of your variables simply refers to the whole list, as you can see from the output of your modified program.
You have not posted the code but this is a very simple issue. When you provide command line arguments python takes it as a list. So when I say
import sys
print sys.argv
Then from the command line i type:
python program.py first second third
the output is what you are getting i.e. all the variables as a list.In order to get the words seperately use list indices. So to get the first argument you use sys.argv[0] which would give program.py
So your code would be like this:
import sys
print 'script name:', sys.argv[0]
print '1st var:', sys.argv[1]
#and so on