python学习笔记，视频day14-集合，字符串格式化

分类：

可变不可变

　　可变：列表，字典

　　不可变：字符串，数字，元组

访问顺序

　　直接访问：数字

　　顺序访问：列表，字符串，元组

　　映射：字典

存放元素个数

　　容器类型：列表，元组，字典

　　原子：数字，字符串

集合：

　　1.不同元素组成

　　2.无序

　　3.元素必须是不可变类型（可哈希的值）

　　交集   intersection    &

　　并集   union     |

　　差集   difference    -

　　交叉补集   symmetric_difference

方法：

#集合
s=set("hello")
print(s)
s=set(["alex","hello"])
print(s)
# 结果
# {'l', 'h', 'e', 'o'}
# {'hello', 'alex'}

# 添加add
s={1,2,3,4,5,6}
s.add(22)
s.add(2)
s.add('3')
print(s)
# 结果
# {1, 2, 3, 4, 5, 6, '3', 22}
s={1,2,3,4,5,6}
s.clear()
print(s)
# 结果
# set()
# 删除，随机
s={1,2,3,4,5,6}
s.pop()
print(s)
# 结果
# {2, 3, 4, 5, 6}
# 指定删除，不存在时会报错
s={1,2,3,4,5,6}
s.remove(2)
print(s)
# 结果
# {1, 3, 4, 5, 6}
# 指定删除，不存在时不会报错
s={1,2,3,4,5,6}
s.discard('22')
print(s)
# 结果
# {1, 2, 3, 4, 5, 6}

# 更新s1，更新多个值
s1={1,2}
s2={3,5,43,1}
print(s1.update(s2),s1,s2)
# print(s1.union(s2),s1,s2)#不更新
# 结果
#None {1, 2, 3, 5, 43} {43, 3, 5, 1}

# 集合可以用来判断关系
python_1=["yangzi","siqi","chenglong","yunqianyue"]
linux_1=["yangzi","daqiao","chenglong"]
p_s=set(python_1)
l_s=set(linux_1)
print(p_s,l_s)
# 交集
print(p_s.intersection(l_s))
print(p_s&l_s)
# 结果
# {'chenglong', 'yangzi'}
# 并集
print(p_s.union(l_s))
print(p_s|l_s)
# 结果
# {'yunqianyue', 'yangzi', 'siqi', 'daqiao', 'chenglong'}
# 差集
print(p_s.difference(l_s))
print(p_s-l_s)
# 结果
# {'yunqianyue', 'siqi'}

# 交叉补集
print(p_s.symmetric_difference(l_s))
# 结果
# {'yunqianyue', 'daqiao', 'siqi'}

python_1=["yangzi","siqi","chenglong","yunqianyue"]
linux_1=["yangzi","daqiao","chenglong"]
p_s=set(python_1)
l_s=set(linux_1)
print(p_s,l_s)
# v=l_s.intersection_update(p_s)
l_s.intersection_update(p_s)
print(p_s,l_s)
# 结果
# None {'yunqianyue', 'yangzi', 'siqi', 'chenglong'} {'yangzi', 'chenglong'}

# 是否有交集，否返回True
s1={1,2}
s2={3,5,43}
print(s1.isdisjoint(s2))
# 结果
# True
# s1是s2的子集,返回True
s1={1,2}
s2={3,5,43,1,2}
print(s1.issubset(s2))
# 结果
# True

补充：

　　集合是可变的，可通过frozenset定义不可变集合

s=frozenset("hello")
print(s)

# 简单去重
names=["yangzi","siqi","chenglong","yunqianyue","siqi"]
s=list(set(names))
print(s)
#结果
#['yunqianyue', 'chenglong', 'yangzi', 'siqi']

 

字符串格式化

常规

　　%拼接，键方式

format用法

 

　　%s    字符串，接受所有

　　%d    数字，只能接受数字

　　%f    小数

补充：

　　sep拼接

# 字符串格式化
msg="i am "+"yang"
print(msg)
# 结果
# i am yang
msg="i am %s hobby is %s"%('yang','swimming')
print(msg)
# 结果
# i am yang hobby is swimming
msg="i am %s hobby is %d"%('yang',22)
print(msg)
# 结果
# i am yang hobby is 22

#打印浮点数
msg="i am %s hobby is %f"%('yang',22.2222223335678)
print(msg)
# # 结果
# # i am yang hobby is 22.222222
# 打印%
msg="i am %s hobby is %2f%%"%('yang',22.2222223335678)
print(msg)
# 结果
# i am yang hobby is 22.222222%

# 键方式
tp1="i am %(name)s hobby is %(bo)s"%{"name":"yang","bo":"Swim"}
print(tp1)
# 结果
# i am yang hobby is Swim

# 右对齐,颜色\033
tp1="i am \033[43:1m%(name)-20s hobby\033[0m is %(bo)s"%{"name":"yang","bo":"Swim"}
print(tp1)
# 结果
# i am yang                 hobby is Swim

# 拼接符
print("root","a","z",sep="-")
# 结果
# root-a-z

format用法

 

# format
# 一一对应
tp1="i am {},age {},hobby {}".format("yang",18,"swim")
print(tp1)
# 结果
# i am yang,age 18,hobby swim
tp1="i am {2},age {0},hobby {1}".format("yang",18,"swim")
print(tp1)
# 结果
# i am swim,age yang,hobby 18

tp1="i am {name},age {a},hobby {h}".format(name="yang",a=15,h="swim")
print(tp1)
# 结果
# i am yang,age 15,hobby swim

tp1="i am {:s},age {:s},hobby {:s}".format(*["a","b","s",2],[222,"g"])
print(tp1)
# 结果
# i am a,age b,hobby s
tp1="i am {name},age {a},hobby {h}".format(**{"name":"yang","a":1,"h":"swim"})
print(tp1)
# 结果
# i am yang,age 1,hobby swim

# :b 二进制，：o八进制
tp1="{:b},{:o},{:d},{:x},{:X},{:%}".format(15,15,15,15,15,15.3334,33,"dd")
print(tp1)
# 结果
# 1111,17,15,f,F,1533.340000%