集合

集合介绍

set 定义空集合：a=set()

{1,2,3,4}

集合中元素必须为不可变对象。可hash对象集合元素是不重复的，唯一的。

集合常用方法

add

给集合新增元素

a = {1, 2, 36, 5564, 14}
a.add(40)
print(a)
# {1, 2, 36, 40, 14, 5564}

update

把原来集合中没有的元素重其他集合导入、更新

a = {1,2,3}
a.update({4,5,6})
print(a)
#{1, 2, 3, 4, 5, 6}

remove

删除集合中元素，如果元素不存在则报错

a = {1,2,3,4, 5, 6}
a.remove(6)
print(a)
#{1, 2, 3, 4, 5}

a = {1,2,3,4, 5, 6}
a.remove(0)
print(a)
#Traceback (most recent call last):
#   File "F:/study/python/code/demo/demo_list.py", line 10, in <module>
#     a.remove(0)
# KeyError: 0

discard

删除集合中的元素，如果元素不存在不报错

a = {1,2,3,4, 5, 6}
a.discard(6)
print(a)
#{1, 2, 3, 4, 5}
a.discard(0)
print(a)
# {1, 2, 3, 4, 5}

set

set的简易用法：删除重复的元素

lst = [1,1,2,3,2,23,45,6,6]
new_lst = list(set(lst))
print(new_lst)
# [1, 2, 3, 6, 45, 23]

集合求交集

a = {1,2,3,4}
b = {4,5,6,7}
print(a & b)
# {4}
print(a.intersection(b))
# {4}

集合求并集

a = {1,2,3,4}
b = {4,5,6,7}
print(a | b)
# {1, 2, 3, 4, 5, 6, 7}
print(a.union(b))
# {1, 2, 3, 4, 5, 6, 7}

集合求差集

a = {1,2,3,4,5,6,7}
b = {4,5,6,7}
print(a - b)
# {1, 2, 3}
print(a.difference(b))
# {1, 2, 3}

元组

元组介绍

元祖只读列表，可循环查询，可切片。儿子不能改，孙子可能可以改

>>> tu = (1,2,3,[1,2,3])
>>> tu[0] = 100
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment
>>> tu[-1][0] = 100
>>> tu
(1, 2, 3, [100, 2, 3])

元组定义

>>> t = ()
>>t
()
>>> print(type(t))
<class 'tuple'>
>>> t = tuple()
>>> t
()
>>> print(type(t))
<class 'tuple'>
>>> t = (1)  此时t是数字类型
>>> print(type(t))
<class 'int'>
>>> t = (1,)
>>> print(type(t))
<class 'tuple'>

元组常用方法

index

查看元素为1的index

>>a = (1,'zc')
>>a.index(1)
0

count

查看元素出现的次数

>>a = (1,'zc')
>>a.count(1)
1

元组和列表之间的相互转换，使用tuple和list方法:

>>a = [1,2,3]
>>b = tuple(a)
>>b
(1, 2, 3)
>>c = list(b)
>>c
[1, 2, 3]

python学习笔记之集合和元组

集合