Python dict 详解

mydict = {"server":"local", "database":"master", "uid":"admin", "pwd":"secret"}

dict是无序的

dict  增加元素

mydict[1] = "test"mydict.setdefault(2,"test2")

注意：setdefault只有在该key不存在的情况下才将该key-value插入dict。如果该key已存在，则setdefault不会修改该key对应的valule，也就是说此时setdefault对dict无任何影响。

dict 删除元素

del(mydict[1])mydict.pop(2)mydict.clear()

dict 查找元素

if "key1" in mydict:    print mydict["key1"]else:    print "None"mydict.get("key1")

注：get时如果该键不存在返回None，不会报错，如果直接下标取值当该键不存在时会报错。

dict 修改元素

mydict["key1"] = "value1"

dict 字典的遍历

for k in mydict:    print "mydict[%s] =" % k,mydict[k]#字典items()的使用#每个元素是一个key和value组成的元组，以列表的方式输出for (k, v) in mydict.items():    print "mydict[%s] =" % k, v#调用iteritems()实现字典的遍历for k, v in mydict.iteritems():    print "mydict[%s] =" % k, vfor (k, v) in zip(mydict.iterkeys(), mydict.itervalues()):    print "mydict[%s] =" % k, v

#输出key的列表print mydict.keys()#输出value的列表print mydict.values()

#字典的更新

dict1 = {"a" : "apple", "b" : "banana"}dict2 = {"b" : "grape", "c" : "orange"}dict1.update(dict2)print dict1 #{'a': 'apple', 'c': 'orange', 'b': 'grape'}print dict2 #{'c': 'orange', 'b': 'grape'}

dict 浅拷贝

dict1 = {"a" : "apple", "b" : {"g" : "grape","o" : "orange"}}dict2 = copy.copy(dict1)#或者使用dict1.copy()print dict2             #{"a" : "apple", "b" : {"g" : "grape","o" : "orange"}}dict2["b"]["o"] = "apple2"print dict2             #{"a" : "apple", "b" : {"g" : "grape","o" : "apple2"}}print dict1             #{"a" : "apple", "b" : {"g" : "grape","o" : "apple2"}}

dict 深拷贝

dict1 = {"a" : "apple", "b" : {"g" : "grape","o" : "orange"}}dict2 = copy.deepcopy(dict1)print dict2             #{"a" : "apple", "b" : {"g" : "grape","o" : "orange"}}dict2["b"]["o"] = "apple2"print dict2             #{"a" : "apple", "b" : {"g" : "grape","o" : "apple2"}}print dict1             #{"a" : "apple", "b" : {"g" : "grape","o" : "orange"}}