added solution for PROB

PROB.py

@@ -0,0 +1,46 @@
+#!/usr/bin/python3
+"""
+Solutions to the PROB Rosalind Problem - Introduction to Random Strings
+Author: Peter Vlasveld
+Date: 20190222
+"""
+import math
+
+#Read in file content into list
+f1 = open("rosalind_prob.txt")
+content = f1.readlines()
+f1.close()
+
+"""
+Function to calculate the probability of the exact sequence given the GC-content
+@param gc - the GC-content given 
+@param seq - the sequence being studied
+
+@return - the raw probability value
+"""
+def calcProb(gc, seq):
+    # get probability for just one nucleotide
+    gchalf = gc/2.0
+    athalf = (1.0-gc)/2.0
+
+    # multiply all of the probability values for each letter in the sequence
+    prob = 1.0
+    for i in range(0, len(seq)):
+        if seq[i] == 'A' or seq[i] == 'T':
+            prob *= athalf
+        elif seq[i] == 'G' or seq[i] == 'C':
+            prob *= gchalf
+    
+    # return the probability value
+    return prob
+
+# take the log of the probabilities returned by calcProb
+# format them to 3 decimal places
+gcCons = content[1].split( )
+finalProbs = []
+for i in gcCons:
+    rawProb = calcProb(float(i), content[0])
+    finalProbs.append("%.3f" % math.log10(rawProb))
+
+# print the probabilities with spaces in between
+print(" ".join(finalProbs))