Python 字典

>>> a = {‘a‘:1,‘b‘:2}
>>> a[‘a‘]
1
>>> b = {‘a‘:[1,2,3],‘b‘:[4,5,6]}
>>> b[‘a‘][2] = 5 #KEY ‘a‘ 的第三个值, 改为5.
>>> b
{‘a‘: [1, 2, 5], ‘b‘: [4, 5, 6]}

>>> a = {2:‘x‘,‘asd‘:‘43‘,(1,2,3):33}
>>> a
{2: ‘x‘, (1, 2, 3): 33, ‘asd‘: ‘43‘}
>>> b = {[1,‘a‘]:"a"}
#列表为可变对象, 不能作为"KEY"
Traceback (most recent call last):
  File "<pyshell#4>", line 1, in <module>
    b = {[1,‘a‘]:"a"}
TypeError: unhashable type: ‘list‘

>>> a = {‘a‘:1,‘b‘:2,‘c‘:3}
>>> a
{‘a‘: 1, ‘c‘: 3, ‘b‘: 2}
>>> a[‘d‘] = 4 #增加‘d‘ KEY
>>> a
{‘a‘: 1, ‘c‘: 3, ‘b‘: 2, ‘d‘: 4}
>>> a.update({‘d‘:44}) #更新‘d‘的值, 增加多个也可以
>>> a
{‘a‘: 1, ‘c‘: 3, ‘b‘: 2, ‘d‘: 44}
>>> a[‘d‘]=88 #修改值
>>> a
{‘a‘: 1, ‘c‘: 3, ‘b‘: 2, ‘d‘: 88}
>>> del a[‘d‘] #删除值
>>> a
{‘a‘: 1, ‘c‘: 3, ‘b‘: 2}
>>> a.pop(‘c‘) #删除值
3
>>> a
{‘a‘: 1, ‘b‘: 2}
>>> a.clear() #清空内容
>>> a
{}

#字典, POP方法, 如果KEY不存在, 可以指定返回值 / LIST不可以
>>> a = {‘a‘:1,‘b‘:2,‘c‘:3}
>>> a.pop(‘d‘)

Traceback (most recent call last):
  File "<pyshell#21>", line 1, in <module>
    a.pop(‘d‘)
KeyError: ‘d‘
>>> a.pop(‘d‘,‘KEY d is not exist‘)
‘KEY d is not exist‘

#集合has_key()方法
>>> a = {‘a‘:1,‘b‘:2,‘c‘:3}
>>> ‘a‘ in a
True
>>> a.has_key(‘b‘) 
True
>>> "a" not in a
False