python中的dict_Python中dict详解

python3.0以上&＃xff0c;print函数应为print()&＃xff0c;不存在dict.iteritems()这个函数。

在python中写中文注释会报错&＃xff0c;这时只要在头部加上# coding&＃61;gbk即可

#字典的添加、删除、修改操作

dict &＃61; {"a" : "apple", "b" : "banana", "g" : "grape", "o" : "orange"}

dict["w"] &＃61; "watermelon"

del(dict["a"])

dict["g"] &＃61; "grapefruit"

print dict.pop("b")

print dict

dict.clear()

print dict

#字典的遍历

dict &＃61; {"a" : "apple", "b" : "banana", "g" : "grape", "o" : "orange"}

for k in dict:

print "dict[%s] &＃61;" % k,dict[k]

#字典items()的使用

dict &＃61; {"a" : "apple", "b" : "banana", "c" : "grape", "d" : "orange"}

#每个元素是一个key和value组成的元组&＃xff0c;以列表的方式输出

print dict.items()

#调用items()实现字典的遍历

dict &＃61; {"a" : "apple", "b" : "banana", "g" : "grape", "o" : "orange"}

for (k, v) in dict.items():

print "dict[%s] &＃61;" % k, v

#调用iteritems()实现字典的遍历

dict &＃61; {"a" : "apple", "b" : "banana", "c" : "grape", "d" : "orange"}

print dict.iteritems()

for k, v in dict.iteritems():

print "dict[%s] &＃61;" % k, v

for (k, v) in zip(dict.iterkeys(), dict.itervalues()):

print "dict[%s] &＃61;" % k, v

#使用列表、字典作为字典的值

dict &＃61; {"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 &＃61; {"a" : "apple", "b" : "banana", "c" : "grape", "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&＃xff0c;以列表的方式输出

print dict.items()

dict &＃61; {"a" : "apple", "b" : "banana", "c" : "grape", "d" : "orange"}

it &＃61; dict.iteritems()

print it

#字典中元素的获取方法

dict &＃61; {"a" : "apple", "b" : "banana", "c" : "grape", "d" : "orange"}

print dict

print dict.get("c", "apple")

print dict.get("e", "apple")

#get()的等价语句

D &＃61; {"key1" : "value1", "key2" : "value2"}

if "key1" in D:

print D["key1"]

else:

print "None"

#字典的更新

dict &＃61; {"a" : "apple", "b" : "banana"}

print dict

dict2 &＃61; {"c" : "grape", "d" : "orange"}

dict.update(dict2)

print dict

#udpate()的等价语句

D &＃61; {"key1" : "value1", "key2" : "value2"}

E &＃61; {"key3" : "value3", "key4" : "value4"}

for k in E:

D[k] &＃61; E[k]

print D

#字典E中含有字典D中的key

D &＃61; {"key1" : "value1", "key2" : "value2"}

E &＃61; {"key2" : "value3", "key4" : "value4"}

for k in E:

D[k] &＃61; E[k]

print D

#设置默认值

dict &＃61; {}

dict.setdefault("a")

print dict

dict["a"] &＃61; "apple"

dict.setdefault("a","default")

print dict

#调用sorted()排序

dict &＃61; {"a" : "apple", "b" : "grape", "c" : "orange", "d" : "banana"}

print dict

#按照key排序

print sorted(dict.items(), key&＃61;lambda d: d[0])

#按照value排序

print sorted(dict.items(), key&＃61;lambda d: d[1])

#字典的浅拷贝

dict &＃61; {"a" : "apple", "b" : "grape"}

dict2 &＃61; {"c" : "orange", "d" : "banana"}

dict2 &＃61; dict.copy()

print dict2

#字典的深拷贝

import copy

dict &＃61; {"a" : "apple", "b" : {"g" : "grape","o" : "orange"}}

dict2 &＃61; copy.deepcopy(dict)

dict3 &＃61; copy.copy(dict)

dict2["b"]["g"] &＃61; "orange"

print dict

dict3["b"]["g"] &＃61; "orange"

print dict

补充&＃xff1a;

1 初始化

>>> d &＃61; dict(name&＃61;&＃39;visaya&＃39;, age&＃61;20)

>>> d &＃61; dict(zip([&＃39;name&＃39;, &＃39;age&＃39;], [&＃39;visaya&＃39;, 20]))

#dict.fromkeys(listkeys, default&＃61;0) 把listkeys中的元素作为key均赋值为value&＃xff0c;默认为0

>>> d &＃61; dict.fromkeys([&＃39;a&＃39;, &＃39;b&＃39;], 1)

>>> d

{&＃39;a&＃39;: 1, &＃39;b&＃39;: 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&＃xff0c;因为不存在重复的项)&＃xff0c;但dict.values()不可以进行如上操作。

>>> k &＃61; d.keys()

>>> k

dict_keys([&＃39;a&＃39;, &＃39;b&＃39;])

>>> list(k)

[&＃39;a&＃39;, &＃39;b&＃39;]

>>> k | {&＃39;x&＃39;: 3}

{&＃39;a&＃39;, &＃39;x&＃39;, &＃39;b&＃39;}

>>> k | {&＃39;x&＃39;}

{&＃39;a&＃39;, &＃39;x&＃39;, &＃39;b&＃39;}

>>> k | {&＃39;x&＃39;, &＃39;y&＃39;}

{&＃39;a&＃39;, &＃39;y&＃39;, &＃39;b&＃39;, &＃39;x&＃39;}

>>> k & {&＃39;x&＃39;}

set()

>>> v &＃61; d.values()

>>> v

dict_values([1, 2])

>>> v | {&＃39;x&＃39;}

Traceback (most recent call last):

File "", line 1, in

TypeError: unsupported operand type(s) for |: &＃39;dict_values&＃39; and &＃39;set&＃39;

3 排序字典键

两种方法:

3.1 sort:

>>> Ks &＃61; list(d.keys())

>>> Ks.sort()

>>> for k in Ks:

...     print(k, d[k])

...

a 1

b 2

3.2 sorted:

>>> for k in sorted(d.keys()):

...     print(k, d[k])

...

a 1

b 2

3.3 注意

>>> for k in list(d.keys()).sort():

...     print(k, d[k])

...

Traceback (most recent call last):

File "", line 1, in

TypeError: &＃39;NoneType&＃39; object is not iterable

出错原因&＃xff1a;

list.sort() list.append()函数都是对自身的操作&＃xff0c;没有返回值&＃xff0c;故需先将list(d.keys())的结果保存下来&＃xff0c;在结果上进行sort()

4 常用函数

4.1 get()

D.get(k[, d])   &＃61;> D[k] if k in D else d. d defaults to none.

4.2 pop()

D.pop(value[, d])   &＃61;> 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] &＃61; E[k]

If E lacks .keys() method, does:     for (k, v) in E: D[k] &＃61; v

In either case, this is followed by: for k in F: D[k] &＃61; F[k]

>>> d &＃61; dict(name&＃61;&＃39;visaya&＃39;, age&＃61;21)

>>> d1&＃61; {&＃39;age&＃39;: 20, &＃39;sex&＃39;: &＃39;male&＃39;}

>>> d2 &＃61; zip([&＃39;a&＃39;, &＃39;b&＃39;], [1, 2])

>>> d.update(d1)

>>> d

{&＃39;age&＃39;: 20, &＃39;name&＃39;: &＃39;visaya&＃39;, &＃39;sex&＃39;: &＃39;male&＃39;}

#for k in d1: d[k] &＃61; d1[k]

>>> d.update(d2)

>>> d

{&＃39;age&＃39;: 20, &＃39;name&＃39;: &＃39;visaya&＃39;, &＃39;sex&＃39;: &＃39;male&＃39;}

#for (k, v) in d2: d[k] &＃61; 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 &＃61; dict()

d &＃61; dict(name&＃61;"nico", age&＃61;23)

d &＃61; dict(([&＃39;name&＃39;, "nico"], [&＃39;age&＃39;, 23]))

当然还有更方便&＃xff0c;简单的

Python代码

d &＃61; {}

d &＃61; {"name":"nico", "age":23}

遍历

通过对key的遍历&＃xff0c;遍历整个dict

Python代码

d &＃61; {"name":"nico", "age":23}

for key in d:

print "key&＃61;%s, value&＃61;%s" % (key, d[key])

for key in d.iterkeys():

print "key&＃61;%s, value&＃61;%s" % (key, d[key])

for key in d.keys():

print "key&＃61;%s, value&＃61;%s" % (key, d[key])

for key in iter(d):

print "key&＃61;%s, value&＃61;%s" % (key, d[key])

for key,item in d.items():

print "key&＃61;%s, value&＃61;%s" % (key, item)

当然也可以直接遍历value

Python代码

d &＃61; {"name":"nico", "age":23}

for value in d.values():

print value

for key,value in d.viewitems():

print "key&＃61;%s, value&＃61;%s" % (key, value)

for value in d.viewvalues():

print "value&＃61;%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&＃xff0c;类似数据库中的view&＃xff0c;当dict改变时&＃xff0c;该view对象也跟着改变

常用方法

Python代码

d &＃61; {"name":"nico", "age":23}

d["name"] &＃61; "aaaa"

d["address"] &＃61; "abcdefg...."

print d   #{&＃39;age&＃39;: 23, &＃39;name&＃39;: &＃39;aaaa&＃39;, &＃39;address&＃39;: &＃39;abcdefg....&＃39;}

获取dict值

Python代码

print d["name"]               #nico

print d.get("name")         #nico

如果key不在dict中&＃xff0c;返回default&＃xff0c;没有为None

Python代码

print d.get("namex", "aaa")       #aaa

print d.get("namex")                  #None

排序sorted()

Python代码

d &＃61; {"name":"nico", "age":23}

for key in sorted(d):

print "key&＃61;%s, value&＃61;%s" % (key, d[key])

#key&＃61;age, value&＃61;23

#key&＃61;name, value&＃61;nico

删除del

Python代码

d &＃61; {"name":"nico", "age":23}

Python代码

del d["name"]

#如果key不在dict中&＃xff0c;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: &＃39;names&＃39;

清空clear()

Python代码

d &＃61; {"name":"nico", "age":23}

d.clear()

print d                                                    #{}

copy()

Python代码

d1 &＃61; d.copy()               #{&＃39;age&＃39;: 23, &＃39;name&＃39;: &＃39;nico&＃39;}

#使用返回view对象

d2 &＃61; d1.viewitems()    #dict_items([(&＃39;age&＃39;, 23), (&＃39;name&＃39;, &＃39;nico&＃39;)])

#修改字典d1&＃xff0c;新增元素

d1["cc"] &＃61; "aaaaaa"

print d2

#dict_items([(&＃39;cc&＃39;, &＃39;aaaaaa&＃39;), (&＃39;age&＃39;, 23), (&＃39;name&＃39;, &＃39;nico&＃39;)])

pop(key[, default])

如果key在dict中&＃xff0c;返回&＃xff0c;不在返回default

Python代码

#如果key在dict中&＃xff0c;返回&＃xff0c;不在返回default

print d.pop("name", "niccco")                #nico

print d.pop("namezzz", "niccco")           #niccco

#key不在dict中&＃xff0c;且default值也没有&＃xff0c;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&＃xff0c;如果字典为空会抛出KeyError

Python代码

d &＃61; {"name":"nico", "age":23}

print d.popitem()       #(&＃39;age&＃39;, 23)

print d.popitem()       #(&＃39;name&＃39;, &＃39;nico&＃39;)

#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&＃xff0c;key重复时将用other中的值覆盖

Python代码

d &＃61; {"name":"nico", "age":23}

d2 &＃61; {"name":"jack", "abcd":123}

d.update(d2)

print d     #{&＃39;abcd&＃39;: 123, &＃39;age&＃39;: 23, &＃39;name&＃39;: &＃39;jack&＃39;}