Add defining functions.

Author: hermite2053

flow/defining_functions/keyword_args.py

@@ -0,0 +1,5 @@
+def print_distance(value, unit='meters'):
+    print("Distance:", value, unit)
+
+print_distance(299792458) # is equal to light travels in 1 second.
+print_distance(220, 'yards') # is equal to 1 Furlong, used in horse racing.