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, v
for (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"}}