Outline for February 22, 2012

Reading: §20

1. Dictionary
   1. Collection of key-value pairs
   2. What a “mapping” is
   3. Mutable
2. Creating dictionaries
   1. Using d = {}
   2. Using d = dict()
3. Methods for dictionaries
   1. k in D: True if dictionary D has key k; else False
   2. D.keys(): list of keys in D
   3. D.values(): list of values in D
   4. D.items(): list of tuples (key, value) in D
   5. D.get(k, d): if key k in D, return associated value; else return d
   6. del D[k]: delete tuple with key k from D
   7. D.clear(): delete all entries in D
4. Example: memos
   1. Recursive Fibonacci [rfibmemo.py]
5. Sorting the dictionary
   1. sorted sorts based on keys
6. Example: word frequency count
   1. Unsorted [wfc-1.py]
   2. Sorted alphabetically [wfc-2.py]
   3. Sorted alphabetically, but dictionary order [wfc-2a.py]
   4. Sorted by frequency [wfc-3.py]
   5. Sorted by frequency first, the alphabetically [wfc-4.py]

ECS 10, Basic Concepts of Computing Winter Quarter 2012