python xx003字典

将2个列表根据元素位置合并成字典：

方法一：

>>> a
['shanghai', 'chengdu', 'shandong']
>>> b
['wo', 'chun', 'bing']
>>> c = dict(zip(a,b))
>>> c
{'shanghai': 'wo', 'chengdu': 'chun', 'shandong': 'bing'}
>>> c['shandong']
'bing'

取2个列表同样位置的元素：

>>> a
['shanghai', 'chengdu', 'shandong']
>>> b
['wo', 'chun', 'bing']
>>> b[a.index('shandong')]
'bing'
>>> 

创建列表

#方法一
>>> dict1 = dict((('a' ,20), ('b' ,30)))
>>> dict1
{'a': 20, 'b': 30}
#方法二：
>>> dict2 = dict('i'='shandong', 'she'='chengdu')
SyntaxError: keyword can't be an expression
>>> dict2 = dict(i='shandong', she='chengdu')
>>> dict2
{'i': 'shandong', 'she': 'chengdu'}
#列表增加元素
>>> dict2['he'] = 'chongqing'
>>> dict2
{'i': 'shandong', 'she': 'chengdu', 'he': 'chongqing'}

#创建字典，指定values为kong
>>> c = dict.fromkeys(('1', '2'), 'kong')
>>> c
{'1': 'kong', '2': 'kong'}
>>> c.values()
dict_values(['kong', 'kong'])
>>> c.items()
dict_items([('1', 'kong'), ('2', 'kong')])
>>> c.keys()
dict_keys(['1', '2'])
#c字典增加key和value
>>> c['3']='duo'
>>> c
{'1': 'kong', '2': 'kong', '3': 'duo'}
>>> 

>>> d = dict.fromkeys((range(5)), 'a')
>>> d
{0: 'a', 1: 'a', 2: 'a', 3: 'a', 4: 'a'}
>>> for key in d.keys():
    print(key)

    
0
1
2
3
4
>>> for value in d.values():
    print(value)

    
a
a
a
a
a
>>> for k, v in d.items():
    print(k, v)

    
0 a
1 a
2 a
3 a
4 a

>>> for k in d.items():
    print(k)

    
(0, 'a')
(1, 'a')
(2, 'a')
(3, 'a')
(4, 'a')

>>> d
{0: 'a', 1: 'a', 2: 'a', 3: 'a', 4: 'a'}
# get取值时如果取的值不存在则返回none，不报错
>>> d.get('5')
>>> print(d.get(5))
None
>>> 4 in d
True
>>> 5in d
False
>>> d.clear()
>>> d
{}
>>> a = {'1':'one', '2':'two', '3':'three'}
# 浅拷贝
>>> b = a.copy()
>>> c = a
>>> a
{'1': 'one', '2': 'two', '3': 'three'}
>>> b
{'1': 'one', '2': 'two', '3': 'three'}
>>> c
{'1': 'one', '2': 'two', '3': 'three'}
>>> c['4']='four'
>>> a
{'1': 'one', '2': 'two', '3': 'three', '4': 'four'}
>>> b
{'1': 'one', '2': 'two', '3': 'three'}
>>> c
{'1': 'one', '2': 'two', '3': 'three', '4': 'four'}
>>> e ={'xiaobai':'dog'}
# 将字典e的元素update到b字典中
>>> b.update(e)
>>> b
{'1': 'one', '2': 'two', '3': 'three', 'xiaobai': 'dog'}

>>> b
{'1': 'one', '2': 'two', '3': 'three', 'xiaobai': 'dog'}
>>> cc =10
>>> dd = 'key'
# update格式为括号内加字典，即d.update({key：value})
>>> b.update({cc:dd})
>>> b
{'1': 'one', '2': 'two', '3': 'three', 'xiaobai': 'dog', 10: 'key'}