本章代码比较多，多敲多记多做多想。
七.字典和集合
1.字典
1.字典的创建
(1)创建字典并赋值
d1 = {}
d2 = {'name':'yyx','age':20}
print(d1)
print(d2)
-----------------------------
{}
{'name': 'yyx', 'age': 20}d3 = {'name':{'number1':'yyx','number':'zzy'},'age':20}
print(d3)
----------------------------------------
{'name': {'number1': 'yyx', 'number': 'zzy'}, 'age': 20}(2)dict函数
d4 = dict()
print(d4)
-----------------------
{}d = dict((['x',1],['y',2]))
print(d)
--------------------------------
{'x':1,'y':2}2.字典的常用操作
(1)字典的访问
#以关键字进行索引计算
dict1 = {'name':'yyx','age':20}
print(dict1['age'])
-----------------------------
20
#字典嵌套字典的关键字索引
dict2 = {'name':{'no1':'yyx','no2':'zzy'},'age':20}
print(dict2['name']['no1'])
----------------------------------------------------
yyx#字典嵌套列表的关键字索引
dict3 = {'name':'yyx','score':[10,20,30,40]}
print(dict3['score'][1])
-----------------------------------------
20
#字典嵌套元组的关键字索引
dict4 = {'name':'yyx','score':(10,20,30,40)}
print(dict4['score'][1])
------------------------------------------
20(2)字典的更新
dict1 = {'name':'yyx','age':20}
dict1['name'] = 'zzy' #修改字典元素
dict1['score'] = [10,20,30,40] #添加一个元素
print(dict1)
----------------------------------------
{'name': 'zzy', 'age': 20, 'score': [10, 20, 30, 40]}(3)字典元素的删除
dict1 = {'a':1,'b':2,'c':3}
del dict1['a']
print(dict1)
-------------------------------
{'b': 2, 'c': 3}del 字典：就删除了该字典
(4)检查字典关键字是否存在
- 关键字 in 字典：值为True，则表示关键字存在于字典中
- 关键字 not in 字典：值为True，则表示关键字不存在于字典中
3.字典的常用方法
(1)fromkeys()
d1 = {}.fromkeys(('x','y'),-1)
print(d1)
------------------------------
{'x': -1, 'y': -1}(2)keys(),values(),items()
d = {'name':'yyx','sex':'man'}
print(d.keys())
print(d.values())
print(d.items())
--------------------------------------
dict_keys(['name', 'sex'])
dict_values(['yyx', 'man'])
dict_items([('name', 'yyx'), ('sex', 'man')])(3)copy(),clear(),pop(key)
d = {'math':10,'english':20,'lisan':30}
d.pop('math')
print(d)
print(d.copy())
print(d.clear())
------------------------------------------
{'english': 20, 'lisan': 30}
{'english': 20, 'lisan': 30}
None(4)get(),pop()
d = {'name':'yyx','sex':'man'}
print(d.get('name','zzy'))
print(d.get('name1','zzy'))
--------------------------------------
yyx
zzy
(5)update()
d1 = {'a':1,'b':2,'c':3}
d2 = {'d':4,'e':5}
d1.update(d2)
print(d1
------------------------------
{'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5}4.字典的遍历
(1)遍历字典的关键字
d1 = {'a':1,'b':2,'c':3}
for key in d1.keys():
print(key)
---------------------------
a
b
c(2)遍历字典的值
d1 = {'a':1,'b':2,'c':3}
for value in d1.values():
print(value)
--------------------------
1
2
3(3)遍历字典的元素
d1 = {'a':1,'b':2,'c':3}
for item in d1.items():
print(item)
---------------------------
('a', 1)
('b', 2)
('c', 3)2.集合
1.集合的创建
s1 = {1,2,3,4,5,6,7,8}
print(s1)
s2 = set('abcdef')
print(s2)
s3 = {1,1,1,1,1}
print(s3)
----------------------------------
{1, 2, 3, 4, 5, 6, 7, 8}
{'c', 'e', 'd', 'f', 'a', 'b'}
{1}注：集合不能有相同的元素
2.集合的常用运算
(1)传统的集合运算
- 计算并集
s = {1,2,3}|{3,4,5}|{'a','b'}
print(s)
--------------------------------
{1, 2, 3, 4, 5, 'a', 'b'}- 计算交集
s = {1,2,3,4,5}&{2,3,4,1,}&{2,1,3,4,2}
print(s)
---------------------------------------
{1, 2, 3, 4}- 计算差集
s = {1,2,3,4,5,6,7,8,9} - {1,2,3,4,5}
print(s)
----------------------------------------
{8, 9, 6, 7}- 计算相异元素
s = {1,2,3,4,5,6,7,8,9} ^ {5,6,7,8,9,10}
print(s)
---------------------------------------
{1, 2, 3, 4, 10}(2)集合的比较
- s1==s2： 相同，True；不同，False
s1 = {4,3,2,1}
s2 = {1,2,3,4}
print(s1 == s2)
----------------------
True- s1!=s2：不同，True；相同，False
s1 = {4,3,2,1}
s2 = {1,2,3,4}
print(s1 != s2)
-----------------------------
False- s1<s2：s1是s2的纯子集，返回True
s1 = {4,3,2,1}
s2 = {1,2,3,4,5,6}
print(s1 < s2)
--------------------------
True- s1<=s2：s1是s2的子集，返回True
s1 = {4,3,2,1}
s2 = {1,2,3,4,5,6}
print(s1 <= s2)
-----------------------
True- s1>s2：s1是s2的纯超集，返回True
s1 = {4,3,2,1}
s2 = {1,2,3,4,5,6}
print(s1 > s2)
---------------------
False- s1>=s2：，s1是s2的超集，返回True
s1 = {4,3,2,1}
s2 = {1,2,3,4,5,6}
print(s1 >= s2)
-------------------------
False3.集合的遍历
s = {10,20,30,40}
t = 0
for x in s:
print(x)
t += x
print(t)
--------------------------
40
10
20
30
1004.集合的常用方法
(1)s1.isdisjoin(s2):如果s1和s2没有共同元素，返回True
s1 = {2,3}
s2 = {1,2,3,4}
print(s1.isdisjoint(s2))
--------------------------
False(2)s1.union(s2,....,sn)并集
(3)s1.intersection(s2,....,sn)交集
(4)s1.difference(s2,....,sn)差集
(5)s,add(x)
s = {1,2,3,4,5}
s.add('abc')
print(s)
----------------------
{1, 2, 3, 4, 5, 'abc'}(6)update(s1,s2,....,sn)
s = {10,20,30}
s.update({1,2,3},{3,4,5},{'a','b'})
print(s)
--------------------------------------
{1, 2, 3, 4, 5, 10, 20, 'b', 'a', 30}(7)s.remove(x)
s = {1,2,3,4,5}
s.remove(4)
print(s)
---------------------
{1, 2, 3, 5}
注：如果x不存在，则报错
(8)s.discard(x)
s = {1,2,3,4,5}
s.discard(4)
print(s)
-----------------------
{1, 2, 3, 5}注：同remove，如果x不存在，也不报错
(9)s.pop()
s = {1,2,3,4,5}
print(s.pop())
--------------------
1(10)s.clear()
s = {1,2,3,4,5}
s.clear()
print(s)
----------------------
set()
