python基本数据类型-字典
1.创建字典
>>> dic = {'k1':'v1','k2':'v2','k3':'v3'}
>>> dic = dict(k1='v1',k2='v2')
2.索引
>>> dic['k1']
'v1'
>>> dic['k2']
'v2'
>>> dic = {'k1':'v1','k2':'v2'}
>>> print(dic.get('k1'))
v1
>>> print(dic.get('k2'))
v2
>>> print(dic.get('k3'))
None
>>> print(dic.get('k3','defaultv'))
defaultv
3.新增
>>> dic['k4'] = 'v4'
>>> dic
{'k3': 'v3', 'k2': 'v2', 'k1': 'v1', 'k4': 'v4'}
>>> dic = {'k1':'v1','k2':'v2'}
>>> dic.update({'k3':'v3'})
>>> print(dic)
{'k2': 'v2', 'k1': 'v1', 'k3': 'v3'}
4.删除
>>> del dic['k4']
>>> dic
{'k3': 'v3', 'k2': 'v2', 'k1': 'v1'}
>>> dic = {'k1':'v1','k2':'v2'}
>>> dic.pop('k1')
'v1'
>>> dic
{'k2': 'v2'}
5.
>>> dic.keys()
['k3', 'k2', 'k1']
>>> dic.values()
['v3', 'v2', 'v1']
>>> dic.items()
[('k3', 'v3'), ('k2', 'v2'), ('k1', 'v1')]
6.循环
>>> for k,v in dic.items():
... print(k,v)
...
('k3', 'v3')
('k2', 'v2')
('k1', 'v1')
7.长度
>>> len(dic) 3
8.清空字典元素
>>> dic = dict(k1='v1',k2='v2')
>>> dic
{'k2': 'v2', 'k1': 'v1'}
>>> dic.clear()
>>> dic
{}
9.
10.有序字典
>>> import collections
>>> dic1 = collections.OrderedDict()
>>> dic1['k1'] = 'v1'
>>> dic1['k2'] = 'v2'
>>> dic1['k3'] = 'v3'
>>> print(dic1)
OrderedDict([('k1', 'v1'), ('k2', 'v2'), ('k3', 'v3')])
>>>
11.删除
>>> dic1 = collections.OrderedDict()
>>> dic1['k1'] = 'v1'
>>> dic1['k2'] = 'v2'
>>> dic1['k3'] = 'v3'
>>> dic1
OrderedDict([('k1', 'v1'), ('k2', 'v2'), ('k3', 'v3')])
>>> dic1.pop('k2')
'v2'
>>> dic1
OrderedDict([('k1', 'v1'), ('k3', 'v3')])
>>> dic1 = collections.OrderedDict()
>>> dic1['k1'] = 'v1'
>>> dic1['k2'] = 'v2'
>>> dic1['k3'] = 'v3'
>>> dic1.popitem()
('k3', 'v3')
>>> dic1.popitem()
('k2', 'v2')
12.move_to_end
>>> dic1 = collections.OrderedDict()
>>> dic1['k1'] = 'v1'
>>> dic1['k2'] = 'v2'
>>> dic1['k3'] = 'v3'
>>> dic1.move_to_end('k2')
>>> dic1
OrderedDict([('k1', 'v1'), ('k3', 'v3'), ('k2', 'v2')])
13.默认字典
>>> dic1 = collections.defaultdict(list)
>>> dic1['k1'].append('a')
>>> print(dic1)
defaultdict(<class 'list'>, {'k1': ['a']})