了解序列以及序列的切片操作
切片：从一个序列中取出一个子序列（字符串，列表，元组均支持）
#对序列进行切片操作 mylist = [0,1,2,3,4,5,6] result = mylist[1:4] print(result) #对元组进行切片 myturple = (0,1,2,3,4,5,6) result2 = myturple[:] result3 = myturple[0:5] print(result2) print(result3) #对str进行切片，从头开始，步长为2 mystr = "01234567" result4 = mystr[::2] print(result4) #对字符串进行切片从头开始到最后结束，步长为-1 #相当于反转 mystr1 = "01234567" result5 = mystr1[::-1] print(result5) #对列表进行切片从3开始到1结束，步长为-1 mylist = [0,1,2,3,4,5,6,7] result = mylist[3:1:-1] print(result) #对元组进行切片，头开始到尾结束步长为-2 myturple = (0,1,2,3,4,5,6) result = myturple[::-2] print(result)
#序列的切片实践
mystr = "万过薪月，员序程马黑来，nohtyP学"
result1 = mystr[::-1]
result = result1[9:14]
print(result)mystr = "万过薪月,员序程马黑来,nohtyP学"
result = mystr.split(",")[1][::-1][1::]
print(result)mystr = "万过薪月,员序程马黑来,nohtyP学"
result = mystr.split(",")[1].replace("来","")[::-1]
print(result)mystr = "万过薪月,员序程马黑来,nohtyP学"
result = mystr[5:10:][::-1]
print(result)
2.set集合 {}
不支持元素的重复
#定义集合
my_set = {"itheima","itcast","itheima","itcast"}
empty_set = set()
#集合学习
#定义集合
my_set = {"itheima","itcast","itheima","itcast"}
empty_set = set()
#添加元素
my_set.add("Python")
#移除元素
# my_set.remove("itheima")
#随机取出一个元素
element = my_set.pop()
print(my_set,element)
#清空集合
my_set.clear()
print(my_set)#取2个集合的差集
set1 = {1,2,3}
set2 = {1,4,5}
set3 = set1.difference(set2)
set4 = set2.difference(set1)
set5 = set3.difference(set4)
print(set1)
print(set2)
print(set3)
print(set4)
print(set5)
"""
#消除集合1中和集合2相同的元素
set1 = {1,2,3}
set2 = {1,4,5}
set1.difference_update(set2)
print(set1)
set1 = {1,2,3}
set2 = {1,4,5}
set2.difference_update(set1)
print(set2)
#合并两个集合 union
set3 = set1.union(set2)
print(set3)
#统计集合数量
#集合是去重的
set1={1,2,3,4,5,6,7,89,1,1,1}
number = len(set1)
print(number)
#集合的遍历
#不支持while循环，不支持下标索引
#支持for循环
set1={1,2,3,4,5,6,7,89,1,1,1}
for element in set1:print(element)
