python学习4:字典常用操作

代码如下：

item1 = [('age',1),('addr','aa')]
item2 = [('age',2),('addr','bb')]
item3 = [('age',3),('addr','cc')]
d1,d2,d3=dict(item1),dict(item2),dict(item3)
items = [('A',d1),('B',d2),('C',d3)]
d = dict(items)
d['D'] = {'age':4,'addr':'dd'}
print d
del d['D']
print d.get('C','can\'t find the key')
print d.get('D','can\'t find the key')
#note different from get()
print d.setdefault('D',{'age':4,'addr':'dd'})
print d

d4 = {}
d4 = dict.fromkeys(['user','machine'],'unknown')
print d4
d4['machine'] = ['m1','m2']
#shallow copy
d5 = d4.copy()
d5['user'] = 'user1'
d5['machine'][1] = 'm3'
print d5
print d4

d6 = {'a':'A','b':'B'}
print d6.items()
print d6.keys()
print d6.values()
print d6.pop('a')
print d6
print d6.popitem()
print d6

打印结果：

{'A': {'age': 1, 'addr': 'aa'}, 'C': {'age': 3, 'addr': 'cc'}, 'B': {'age': 2, 'addr': 'bb'}, 'D': {'age': 4, 'addr': 'dd'}}
{'age': 3, 'addr': 'cc'}
can't find the key
{'age': 4, 'addr': 'dd'}
{'A': {'age': 1, 'addr': 'aa'}, 'C': {'age': 3, 'addr': 'cc'}, 'B': {'age': 2, 'addr': 'bb'}, 'D': {'age': 4, 'addr': 'dd'}}
{'machine': 'unknown', 'user': 'unknown'}
{'machine': ['m1', 'm3'], 'user': 'user1'}
{'machine': ['m1', 'm3'], 'user': 'unknown'}
[('a', 'A'), ('b', 'B')]
['a', 'b']
['A', 'B']
A
{'b': 'B'}
('b', 'B')
{}