Question

I’m writing a script where I extract command line arguments using getopt, qualify the values offered, then use those values as limits on a loop. Code fragment is below:

try:
    start_pod, end_pod, topo_value = map(int, args)
except ValueError, error_msg:
    if 'invalid' in str(error_msg):
        err_funct('Non-integer values supplied: {%s}' % args)
    else:
        err_funct(error_msg)

for pod in range(start_pod, end_pod):
    print 'value of pod: %s' % pod
    for switch in range(1,5):
        print 'value of switch: %s' % switch

The problem I am having is with the ‘range’ function. I think I am passing it integers (the map function is converting a list of strings to integers) and if I wasn’t my try/except handler exits by way of an error function I wrote, but for some reason this isn’t working.

If I call my script with the correct number of inputs, e.g. ‘some_script.py 1 1 5’, the script returns nothing.

Answer 1

Your call of the script is incorrect:

>>> range(1,1)
[]

(start_pod and end_pod will both be 1).

The range(i,j) functions returns the following list [i, i + 1, .., j - 1]. Or, differently put, the end point is always removed.

Try changing the for pod in range... line in:

for pod in range(start_pod, end_pod + 1):