added exercise 18

Author: mwarkentin

ex18.py

@@ -0,0 +1,21 @@
+# this one is like your scripts with argv
+def print_two(*args):
+    arg1, arg2 = args
+    print "arg1: %r, arg2: %r" % (arg1, arg2)
+    
+# ok, that *args is actually pointless, we can just do this
+def print_two_again(arg1, arg2):
+    print "arg1: %r, arg2: %r" % (arg1, arg2)
+    
+# this just takes one argument
+def print_one(arg1):
+    print "arg1: %r" % arg1
+    
+# this one takes no arguments
+def print_none():
+    print "I got nothin'."
+    
+print_two("Zed","Shaw")
+print_two_again("Zed","Shaw")
+print_one("First!")
+print_none()