笨方法学python(本文为阅读时从此书摘录的笔记) 第五天

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字典和列表的不同在于，它的索引可以是任意类型的

>>> haha={'a':1,'b':2,'c':3}
>>> print(haha['a'])
1
>>> print(haha['b'])
2
>>> print(haha['c'])
3
>>> haha['d']=4  #在字典中添加元素
>>> print(haha['d'])
4
>>> print(haha)  #输出字典
{'b': 2, 'c': 3, 'd': 4, 'a': 1}

还有这种操作：

>>> haha[1]='sb'
>>> haha[2]='SB'
>>> print(haha)
{1: 'sb', 2: 'SB', 'c': 3, 'b': 2, 'd': 4, 'a': 1}

删除字典中的元素：关键字del

>>> print(haha)
{1: 'sb', 2: 'SB', 'c': 3, 'b': 2, 'd': 4, 'a': 1}
>>> del haha['a']
>>> print(haha)
{1: 'sb', 2: 'SB', 'c': 3, 'b': 2, 'd': 4}
>>> del haha[1]
>>> print(haha)
{2: 'SB', 'c': 3, 'b': 2, 'd': 4}

这是一个重要的例题

cities = {'CA': 'San Francisco', 'MI': 'Detroit','FL': 'Jacksonville'}
cities['NY'] = 'New York'
cities['OR'] = 'Portland'

def find_city(themap, state):
    if state in themap:  #看最后的例子
        return themap[state]
    else:
        return "Not found."

cities['_find'] = find_city  #这里把函数名当做变量，如果这句写在函数之前就会报错

while True:
    print "State? (ENTER to quit)",
    state = raw_input("> ")

    if not state: break   #当没有录入时state为''或者None此时not state为True

    city_found = cities['_find'](cities, state)
    print city_found

>>> not ''
True
>>> not 123
False
>>> not'12'
False
>>> not None
True

>>> haha={'a':1,'b':2,'c':3}
>>> 'a' in haha
True