I'd be a lot more inclined to respond to this if I didn't need to calculate probability values (ie. could input weights instead, which were then normalized.)

To that end, here is a simple Python script which normalizes a list of weights (given as commandline arguments) into a list of probabilities:

#!/usr/bin/python
import sys
weights = [float(v) for v in sys.argv[1:]]
total_w = sum(weights)
probs = [v / total_w for v in weights]
print ('Probabilities : %s' % (", ".join([str(v) for v in probs])))

Produces output like this:

Probabilities : 0.1, 0.2, 0.3, 0.4