command line arguments

[TMS]

Let's say I want to call one of my modules from the command line, for instance I have this find_root(f,xLo, xHi, eps) assignment I've been working on.

I have the header that looks like this:

import sys
 
sys.argv[1,2,3,4]
 
 

Wouldn't that be enough that when I go to a terminal screen (Ubuntu) or console (windows) I could simply type:

find_root.py find_root('x**2 - 2, 0, 3, .0001) and it would work? Assuming that my arguments and the function itself is correct. I'm only looking at the command line arguments right now.

Thank you

[bvdet]

Let's say I want to call one of my modules from the command line, for instance I have this find_root(f,xLo, xHi, eps) assignment I've been working on.

I have the header that looks like this:

import sys
 
sys.argv[1,2,3,4]
 
 

Wouldn't that be enough that when I go to a terminal screen (Ubuntu) or console (windows) I could simply type:

find_root.py find_root('x**2 - 2, 0, 3, .0001) and it would work? Assuming that my arguments and the function itself is correct. I'm only looking at the command line arguments right now.

Thank you

This works at the windows command prompt:

C:\>python find_root.py x**2-4 3 0 0.0001

...function definition....
 
if __name__ == '__main__':
    import sys
    find_root(sys.argv[1], float(sys.argv[2]), float(sys.argv[3]), float(sys.argv[4]))
 

At the python command line:

from find_root import find_root
find_root('x**2-4', 3, 0, 0.0001)

Is there another way?

[bartonc]

This works at the windows command prompt:

C:\>python find_root.py x**2-4 3 0 0.0001

...function definition....
 
if __name__ == '__main__':
    import sys
    find_root(sys.argv[1], float(sys.argv[2]), float(sys.argv[3]), float(sys.argv[4]))
 

At the python command line:

from find_root import find_root
find_root('x**2-4', 3, 0, 0.0001)

Is there another way?

...function definition....
 
if __name__ == '__main__':
    import sys
    find_root(sys.argv[1], float(sys.argv[2]), float(sys.argv[3]), float(sys.argv[4]))
 

is not quite complete because errors will be thrown when too few arguments a sent from the command line or if those arguments can't be converted to float. Most command line scripts will provide help when this happens. Elaborate on this idea:

...function definition....
 
if __name__ == '__main__':
    import sys
    try:
        find_root(sys.argv[1], float(sys.argv[2]), float(sys.argv[3]), float(sys.argv[4]))
    except (IndexError, TypeError):
        print "Usage: Too few arguments"
 

It's a little nicer than showing a python traceback.

[TMS]

Thank you! Good information.

TMS

[bvdet]

I have a suggestion for a slight improvement. If you find that you are entering in the same value for 'eps' consistently, add a default to the function argument list:

def find_root(f, xLo, xHi, eps=0.00001):
..................
..................

Then the function call could be:

find_root('5*x**3+2*x**2-x+1', -3, 4)
# if you need a value for eps different from the default
find_root('5*x**3+2*x**2-x+1', -3, 4, .001)