Python arguments to variables

Question

I am new to python and working on putting arguments into variables. I was trying to only allow three variables as arguments and put them into a, b and c as a string.

#!/usr/bin/python
import sys
x = sys.argv[1:]
x = ' '.join(x)
if len(x) > 3:
 print "Only three arguments"
else:
 print "Too many arguments"
a,b,c=[[y] for y in x.split()]
print a
print b
print c

• Texom512: Why that's print "Too many arguments" if there's less 3???
• Jon Clements: Are you expecting exactly 3 arguments, or up to 3?

Answer 1

Since you want the arguments as scalars, you don't need the [] around y:

a,b,c = [y for y in x.split()]

But frankly, you don't even need to go through the joining a splitting - you can assign an array to a series of comma-delimited scalars:

a,b,c = sys.argv[1:]

Similarly, you shouldn't check len on a joined string, but on the array. A complete example:

#!/usr/bin/python
import sys
x = sys.argv[1:] # no joining!
if len(x) == 3:
 print "Only three arguments"
 a,b,c = x
 print a
 print b
 print c
else:
 print "Too many arguments"

• user4647247: Oh right, thanks! How can I test with a if to check that it's only three arguments and not less ore more.
• jolvi: You can just check len(sys.argv).
• Mureinik: @Iknowpython you can use the == operator. See my edited post.

Answer 2

#!/usr/bin/python
import sys
if len(sys.argv)!=4:
 print "Need to get 3 arguments"
 sys.exit()
a=str(sys.argv[1])
b=str(sys.argv[2])
c=str(sys.argv[3])
print a
print b
print c

• user4647247: If I enter four arguments I get "Only three arguments" thats wrong.

Answer 3

Here's the working code:

import sys
args = sys.argv[1:]
if len(args) > 3:
 print "Too many arguments"
for arg in args:
 print(arg)