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Python中的字典详解

发布时间:2019-02-10 发布网站:脚本之家
脚本之家收集整理的这篇文章主要介绍了Python中的字典详解脚本之家小编觉得挺不错的,现在分享给大家,也给大家做个参考。

-----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:\workspace\project\pydev\src\ddd\ddddd.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'} 

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