--- a/genetrack_util.py	Wed Nov 18 08:12:35 2015 -0500
+++ b/genetrack_util.py	Sat Nov 21 08:57:17 2015 -0500
@@ -6,6 +6,9 @@
 import sys
 import tempfile
 
+GFF_EXT = 'gff'
+SCIDX_EXT = 'scidx'
+
 ROMAN = ['0', 'I', 'II', 'III', 'IV', 'V', 'VI', 'VII', 'VIII', 'IX', 'X',
          'XI', 'XII', 'XIII', 'XIV', 'XV', 'XVI', 'XVII', 'XVIII', 'XIX', 'XX',
          'XXI', 'XXII', 'XXIII', 'XXIV', 'XXV', 'XXVI', 'XXVII', 'XXVIII', 'XXIX',
@@ -104,14 +107,14 @@
             return False
         try:
             [int(i) for i in line[1:]]
-            self.format = 'ssccidx'
+            self.format = SCIDX_EXT
             return True
         except ValueError:
             try:
                 if len(line) < 6:
                     return False
                 [int(line[4]), int(line[5])]
-                self.format = 'gff'
+                self.format = GFF_EXT
                 return True
             except ValueError:
                 return False
@@ -130,7 +133,7 @@
             pass
 
     def parse_line(self, line):
-        if self.format == 'ssccidx':
+        if self.format == SCIDX_EXT:
             return [int(line[1]), int(line[2]), int(line[3])]
         else:
             return [int(line[3]), line[6], line[5]]
@@ -170,7 +173,7 @@
         return data
 
     def add_read(self, read):
-        if self.format == 'ssccidx':
+        if self.format == SCIDX_EXT:
             self.data.append(read)
         else:
             index, strand, value = read