added REVP solution

REVP.py

@@ -0,0 +1,50 @@
+#!/usr/bin/python
+
+#Solution to REVP Rosalind problem - Locating Restriction Sites
+#Author: Peter Vlasveld
+
+#read in file and get contents
+f1 = open("rosalind_revp.txt")
+content = f1.readlines()
+f1.close()
+
+#get DNA string from content
+DNAStr = ""
+for i in xrange(1,len(content)):
+    DNAStr += content[i].strip()
+
+#function to return the DNA compliment
+def DNACompliment(stri):
+	rev = stri[::-1]
+	revList = list(rev)
+	for i in xrange(0, len(revList)):
+		if revList[i] == "A":
+			revList[i] = "T"
+		elif revList[i] == "T":
+			revList[i] = "A"
+		elif revList[i] == "G":
+			revList[i] = "C"
+		elif revList[i] == "C":
+			revList[i] = "G"
+	revCompStr = "".join(revList)
+	return revCompStr
+
+#loop through DNA string
+indexes = []
+lengths = []
+for j in xrange(0, len(DNAStr)-3):
+	#evaluating 4 to 12 character sets, taking the reverse compliment and comparing,
+	#if a match is found record the index and length and then break
+	for k in xrange(4, 13):
+		comp = DNACompliment(DNAStr[j:j+k])
+		if comp == DNAStr[j:j+k]:
+			indexes.extend([j+1])
+			lengths.extend([k])
+			print(DNAStr[j:j+k])
+			break
+
+#output results to a file
+f2 = open("output.txt","w")			
+for i in xrange(0,len(indexes)):
+	f2.write(str(indexes[i]) + " " + str(lengths[i]) + "\n")
+f2.close()