Python中的字典详解

-----python中的数据类型

-----python中的字符串操作

python3.0以上，print函数应为print（），不存在dict.iteritems()这个函数。

在python中写中文注释会报错，这时只要在头部加上# coding=gbk即可

#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 dictdict.clear()print dict#字典的遍历dict = {"a" : "apple","o" : "orange"}for k in dict:? ? print "dict[%s] =" % k,dict[k]#字典items()的使用dict = {"a" : "apple","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","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","d" : "orange"}print dict.iteritems()for k,v in dict.iteritems():? ? print "dict[%s] =" % k,vfor (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","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","d" : "orange"}it = dict.iteritems()print it#字典中元素的获取方法dict = {"a" : "apple","d" : "orange"}print dictprint 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 dictdict2 = {"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keyD = {"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 dictdict["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 copydict = {"a" : "apple","b" : {"g" : "grape","o" : "orange"}}dict2 = copy.deepcopy(dict)dict3 = copy.copy(dict)dict2["b"]["g"] = "orange"print dictdict3["b"]["g"] = "orange"print dict1 初始化>>> d = dict(name='visaya',age=20)>>> d = dict(zip(['name','age'],['visaya',20]))#dict.fromkeys(listkeys,default=0) 把listkeys中的元素作为key均赋值为value，默认为0>>> d = dict.fromkeys(['a','b'],1)>>> d{'a': 1,'b': 1}2 字典视图和几何dict.keys()类似信使可以进行交集和并集等集合操作（类似集合，因为不存在重复的项），但dict.values()不可以进行如上操作。>>> k = d.keys()>>> kdict_keys(['a','b'])>>> list(k)['a','b']>>> k | {'x': 3}{'a','x','b'}>>> k | {'x'}{'a','b'}>>> k | {'x','y'}{'a','y','b','x'}>>> k & {'x'}set()>>> v = d.values()>>> vdict_values([1,2])>>> v | {'x'}Traceback (most recent call last):? File "",line 1,in TypeError: unsupported operand type(s) for |: 'dict_values' and 'set'3 排序字典键两种方法:3.1 sort:>>> Ks = list(d.keys())>>> Ks.sort()>>> for k in Ks:... ? ? print(k,d[k])...?a 1b 23.2 sorted:>>> for k in sorted(d.keys()):... ? ? print(k,d[k])...?a 1b 23.3 注意>>> for k in list(d.keys()).sort():... ? ? print(k,d[k])...?Traceback (most recent call last):? File "",in TypeError: 'NoneType' object is not iterable出错原因：list.sort() list.append()函数都是对自身的操作，没有返回值，故需先将list(d.keys())的结果保存下来，在结果上进行sort()4 常用函数4.1 get()D.get(k[,d]) ? => D[k] if k in D else d. d defaults to none.4.2 pop()D.pop(value[,d]) ? => Remove specified key and return the corresponding value. If key is not found,d is returned if given,otherwise KeyError is raised.4.3 udpate()? ? D.update(E,**F) -> None. ?Update D from dict/iterable E and F.? ? If E has a .keys() method,does: ? ? for k in E: D[k] = E[k]? ? If E lacks .keys() method,does: ? ? for (k,v) in E: D[k] = v? ? In either case,this is followed by: for k in F: D[k] = F[k]>>> d = dict(name='visaya',age=21)>>> d1= {'age': 20,'sex': 'male'}>>> d2 = zip(['a',[1,2])>>> d.update(d1)>>> d{'age': 20,'name': 'visaya','sex': 'male'}#for k in d1: d[k] = d1[k]>>> d.update(d2)>>> d{'age': 20,'sex': 'male'}#for (k,v) in d2: d[k] = v4.4 del()del D[key]4.5 clear()4.6 copy()Python中的dict初始化构造方法创建Python代码 ?d = dict() ?d = dict(name="nico",age=23) ?d = dict((['name',"nico"],['age',23])) ??当然还有更方便，简单的Python代码 ?d = {} ?d = {"name":"nico","age":23} ???遍历通过对key的遍历，遍历整个dict?Python代码 ?d = {"name":"nico","age":23} ?for key in d: ?? ? print "key=%s,value=%s" % (key,d[key]) ?? ? ??for key in d.iterkeys(): ?? ? print "key=%s,d[key]) ?? ? ??for key in d.keys(): ?? ? print "key=%s,d[key]) ?? ? ??for key in iter(d): ?? ? print "key=%s,d[key]) ?? ? ??for key,item in d.items(): ?? ? print "key=%s,item) ???当然也可以直接遍历value?Python代码 ?d = {"name":"nico","age":23} ?for value in d.values(): ?? ? print value ?? ? ??for key,value in d.viewitems(): ?? ? print "key=%s,value) ???for value in d.viewvalues(): ?? ? print "value=%s" % (value) ?这里values和viewvalues的区别?后者返回的是该字典的一个view对象，类似数据库中的view，当dict改变时，该view对象也跟着改变??Python代码 ?d = {"name":"nico","age":23} ?d["name"] = "aaaa" ?d["address"] = "abcdefg...." ?print d ? #{'age': 23,'name': 'aaaa','address': 'abcdefg....'} ???获取dict值Python代码 ?print d["name"] ? ? ? ? ? ? ? #nico ?print d.get("name") ? ? ? ? #nico ???如果key不在dict中，返回default，没有为NonePython代码 ?print d.get("namex","aaa") ? ? ? #aaa ?print d.get("namex") ? ? ? ? ? ? ? ? ?#None ??排序sorted()Python代码 ?d = {"name":"nico","age":23} ?for key in sorted(d): ?? ? print "key=%s,d[key]) ?#key=age,value=23 ?#key=name,value=nico ???删除delPython代码 ?d = {"name":"nico","age":23} ?Python代码 ?del d["name"] ?#如果key不在dict中，抛出KeyError ?del d["names"] ?Python代码 ?Traceback (most recent call last): ?? File "F:workspaceprojectpydevsrcdddddddd.py",line 64,in ?? ? del d["names"] ?KeyError: 'names' ???清空clear()Python代码 ?d = {"name":"nico","age":23} ?d.clear() ?print d ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?#{} ??copy()Python代码 ?d1 = d.copy() ? ? ? ? ? ? ? #{'age': 23,'name': 'nico'} ?#使用返回view对象 ?d2 = d1.viewitems() ? ?#dict_items([('age',23),('name','nico')]) ?#修改字典d1，新增元素 ?d1["cc"] = "aaaaaa" ??print d2 ? ? ? ? ? ? ? ? ??#dict_items([('cc','aaaaaa'),('age','nico')]) ???pop(key[,default])如果key在dict中，返回，不在返回defaultPython代码 ?#如果key在dict中，返回，不在返回default ?print d.pop("name","niccco") ? ? ? ? ? ? ? ?#nico ?print d.pop("namezzz","niccco") ? ? ? ? ? #niccco ?#key不在dict中，且default值也没有，抛出KeyError ?print d.pop("namezzz") ? ? ? ? ? ? ? ? ? ? ? ? #此处抛出KeyError ??popitem()删除并返回dict中任意的一个(key,value)队，如果字典为空会抛出KeyErrorPython代码 ?d = {"name":"nico","age":23} ?print d.popitem() ? ? ? #('age',23) ?print d.popitem() ? ? ? #('name','nico') ?#此时字典d已为空 ?print d.popitem() ? ? ?#此处会抛出KeyError ??update([other])将字典other中的元素加到dict中，key重复时将用other中的值覆盖Python代码 ?d = {"name":"nico","age":23} ?d2 = {"name":"jack","abcd":123} ?d.update(d2) ?print d ? ? #{'abcd': 123,'age': 23,'name': 'jack'}?