python学习——核心语法三

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#set集合
#特点：不可重复，无序，可修改
#由于集合是无序的，因此是不支持索引访问的

s1 = {"C","D","X","T","O","C"}

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#定义空集合 不能用{}，{}表示的是空字典
s2 = set()
s3 = {}
print(s1)
print(type(s2))
print(type(s3))

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s4 = {1,2,3,4,5}
s5 = {2,3,4,7,9}
s4.add(6)
print(s4)
s4.remove(4)
print(s4.pop())

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s4 = {1,2,3,4,5}
#set pop()是按某种顺序进行的，而不是随机的。并且每次执行的结果都一样。
print(s4.union(s5))
print(s4.difference(s5))
print(s4.intersection(s5))  #也可以用 & 符号

french_set = {"张三","许木","王鹏","邓江","胡图","李明","周刚"}

art_set = {"刘梅","王鹏","谢娜","李明","刘强"}

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#同时选修了法语和艺术的学生名单
fa_art_set = french_set.intersection(art_set)
print(fa_art_set)
print(french_set & art_set)

#选修了法语，没有选修艺术的学生
fr_not_ar = french_set.difference(art_set)   # 差集，也可以用 “-”
fr_art_not_ar2 = french_set - art_set
print(fr_not_ar)
print(fr_art_not_ar2)

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french_set = {"张三","许木","王鹏","邓江","胡图","李明","周刚"}

art_set = {"刘梅","王鹏","谢娜","李明","刘强"}

math_set = {"张三","乔九","许木","大大","葛优","王鹏"}
#方式三---->集合推导式的方式
fr_art_not_ar3 = {s for s  in french_set if s not in art_set}
print(fr_art_not_ar3)

#3.统计每个学生选修的课程数量
all_set = french_set.union(art_set)  # 并集，也可以用 “|”
all_set2 = french_set | art_set
print(all_set)  #获取到所有学生，去重
print(all_set2)

all_list = [*french_set, *art_set, *math_set]  #利用list列表可以重复的特性，“*”解包
for student in all_set:
    count = all_list.count(student)
    print(f"{student}\t 选修了 {count} 门课程")


#总结：
# set 集合运算符
#交集  intersection &
#差集  difference   -
#并集  union        |
#解包  *
#集合推导式写法 set = {i表达式 for i in 集合}
#集合推导式写法 set = {i表达式 for i in 集合 if 条件}