概述
一个key可以对应一个多个value。合理的使用字典能给我们编程带来很大的方便。
-----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 2
3.2 sorted:>>> for k in sorted(d.keys()):... print(k,d[k])... a 1b 2
3.3 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] = v
4.4 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
方法 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'}
总结
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