字典（dict)

定义

In [4]: dt1 = {'name':'ray','age':18,'height':175}                              

In [5]: dt1
Out[5]: {'name': 'ray', 'age': 18, 'height': 175}

In [40]: d = {}.fromkeys(('name','tearch'),'ray')
...:

In [41]: d
Out[41]: {'name': 'ray', 'tearch': 'ray'}

In [44]: d = {}.fromkeys(city,code)

In [45]: d
Out[45]: {'bj': [1, 2, 3], 'sh': [1, 2, 3], 'sz': [1, 2, 3]}

In [6]: dt2 = dict(name='ray',age=18,height=175)                                

In [7]: dt2
Out[7]: {'name': 'ray', 'age': 18, 'height': 175}

获取元素

In []: dt1.get('emial','没有这个键')
Out[]: '没有这个键'

In [14]: dt1.get('name')    # 不存在返回none
Out[14]: 'ray'

In [16]: dt1['name']        # 不存在报错
Out[16]: 'ray'

In []: dt1.keys()
Out[]: dict_keys(['name', 'age', 'height'])

In []: dt1.values()
Out[]: dict_values(['ray', , ])

In []: dt1.items()
Out[]: dict_items([('name', 'ray'), ('age', ), ('height', )])

增加元素

In [28]: dt1['weight']=70                                                       

In [29]: dt1
Out[29]: {'name': 'ray', 'age': 18, 'height': 175, 'weight': 70}

In [43]: dt2.setdefault('weight',70)                         # 有则显示，无则添加
Out[43]: 70

In [44]: dt2
Out[44]: {'name': 'ray', 'age': 18, 'height': 175, 'weight': 70}

修改元素

In [30]: dt1['height']=170                                                      

In [31]: dt1
Out[31]: {'name': 'ray', 'age': 18, 'height': 170, 'weight': 70}

In [32]: other={'hobby':['sports','beautiful girls']}                           

In [33]: dt1.update(other)                                                      

In [34]: dt1
Out[34]:
{'name': 'ray',
 'age': 18,
 'height': 170,
 'weight': 70,
 'hobby': ['sports', 'beautiful girls']}

删除

In [36]: dt1.pop('weight','no such key')
Out[36]: 70

In [37]: dt1.popitem()
Out[37]: ('hobby', ['sports', 'beautiful girls'])

In [38]: dt1
Out[38]: {'name': 'ray', 'age': 18, 'height': 170}

In [39]: dt1.clear()                                                            

In [40]: dt1
Out[40]: {}

循环获取

In [54]: for k,v in dt2.items():
    ...:     print(k,v) 

In [56]: for i in dt2:
    ...:     print(i)
    ...: 

删除

del d_name[key]