P59
字典方法
1. clear
2. copy, deepcopy
3. fromkeys
4. get 比下标安全
5. has_key
6. items, iteritems
7. keys, iterkeys
8. pop
9. popitem
10. setdefault
11. update
12. values, itervalues
P59
字典方法
1. clear
2. copy, deepcopy
3. fromkeys
4. get 比下标安全
5. has_key
6. items, iteritems
7. keys, iterkeys
8. pop
9. popitem
10. setdefault
11. update
12. values, itervalues