Upgraded the script with command line argument modules

calcgc.py

 #!/usr/bin/env python
-import sys
+import argparse
 
 # Python programming course
 # Author: Marc van Driel
@@ -31,7 +31,14 @@ def calc_gc_perc(seq):
         return 0.0
 
 if __name__ == '__main__':
-    inpseq = sys.argv[1]
+    # Create our argument parser object.
+    parser = argparse.ArgumentParser()
+    # Add the expected argument.
+    parser.add_argument('input_seq', type=str,
+                        help="Input sequence")
+    # Do the actual parsing.
+    args = parser.parse_args()
+    # And show the output.
     print "The sequence '{}' has %GC of {:.2f}".format(
-              inpseq, calc_gc_perc(inpseq))
- 
+              args.input_seq,
+              calc_gc_percent(args.input_seq))