python中dict的用法

#字典的添加、删除、修改操作

dict = {"a" : "apple", "b" : "banana", "g" : "grape", "o" : "orange"}

dict["w"] = "watermelon"

del(dict["a"])

dict["g"] = "grapefruit"

print dict.pop("b")

print dict

dict.clear()

print dict

#字典的遍历

dict = {"a" : "apple", "b" : "banana", "g" : "grape", "o" : "orange"}

for k in dict:

print "dict[%s] =" % k,dict[k]

#字典items()的使用

dict = {"a" : "apple", "b" : "banana", "c" : "grape", "d" : "orange"}

#每个元素是一个key和value组成的元组，以列表的方式输出

print dict.items()

#调用items()实现字典的遍历

dict = {"a" : "apple", "b" : "banana", "g" : "grape", "o" : "orange"}

for (k, v) in dict.items():

print "dict[%s] =" % k, v

#调用iteritems()实现字典的遍历

dict = {"a" : "apple", "b" : "banana", "c" : "grape", "d" : "orange"}

print dict.iteritems()

for k, v in dict.iteritems():

print "dict[%s] =" % k, v

for (k, v) in zip(dict.iterkeys(), dict.itervalues()):

print "dict[%s] =" % k, v

#使用列表、字典作为字典的值

dict = {"a" : ("apple",), "bo" : {"b" : "banana", "o" : "orange"}, "g" : ["grape","grapefruit"]}

print dict["a"]

print dict["a"][0]

print dict["bo"]

print dict["bo"]["o"]

print dict["g"]

print dict["g"][1]

dict = {"a" : "apple", "b" : "banana", "c" : "grape", "d" : "orange"}

#输出key的列表

print dict.keys()

#输出value的列表

print dict.values()

#每个元素是一个key和value组成的元组，以列表的方式输出

print dict.items()

dict = {"a" : "apple", "b" : "banana", "c" : "grape", "d" : "orange"}

it = dict.iteritems()

print it

#字典中元素的获取方法

dict = {"a" : "apple", "b" : "banana", "c" : "grape", "d" : "orange"}

print dict

print dict.get("c", "apple")

print dict.get("e", "apple")

#get()的等价语句

D = {"key1" : "value1", "key2" : "value2"}

if "key1" in D:

print D["key1"]

else:

print "None"

#字典的更新

dict = {"a" : "apple", "b" : "banana"}

print dict

dict2 = {"c" : "grape", "d" : "orange"}

dict.update(dict2)

print dict

#udpate()的等价语句

D = {"key1" : "value1", "key2" : "value2"}

E = {"key3" : "value3", "key4" : "value4"}

for k in E:

D[k] = E[k]

print D

#字典E中含有字典D中的key

D = {"key1" : "value1", "key2" : "value2"}

E = {"key2" : "value3", "key4" : "value4"}

for k in E:

D[k] = E[k]

print D

#设置默认值

dict = {}

dict.setdefault("a")

print dict

dict["a"] = "apple"

dict.setdefault("a","default")

print dict

#调用sorted()排序

dict = {"a" : "apple", "b" : "grape", "c" : "orange", "d" : "banana"}

print dict

#按照key排序

print sorted(dict.items(), key=lambda d: d[0])

#按照value排序

print sorted(dict.items(), key=lambda d: d[1])

#字典的浅拷贝

dict = {"a" : "apple", "b" : "grape"}

dict2 = {"c" : "orange", "d" : "banana"}

dict2 = dict.copy()

print dict2

#字典的深拷贝

import copy

dict = {"a" : "apple", "b" : {"g" : "grape","o" : "orange"}}

dict2 = copy.deepcopy(dict)

dict3 = copy.copy(dict)

dict2["b"]["g"] = "orange"

print dict

dict3["b"]["g"] = "orange"

print dict