【Python】可变序列和不可变序列的通用操作

可变序列和不可变序列的通用操作

• 判断值是否属于序列：in / not in

m = list(range(10)) # [0,1,2,3,4,5,6,7,8,9,10]
2 in m # True
20 in m # False
name = "apple"
"m" in name # False
"a" in name # True

• 序列链接与重复："+" "*"

m = [1,2,3] + ["a","b","c"]  # [1,2,3,'a','b','c']
x = [1,2,3,4]
y = list(range(3))
z = x + y # [1,2,3,4,0,1,2]
x*3 # [1,2,3,4,1,2,3,4,1,2,3,4]

• 下标索引及切片
  x = [1,2,3,4,5,6,7,8]
  下标索引：x[1],x[2],x[-1]
  切片：x[:5],x[2:5],x[3:],x[:-1]

x = [0,1,2,3,4,5,6,7,8]
x[1] # 1
x[2] # 2
x[-1] # 7
x[:5] # [0,1,2,3,4]
x[2:5] # [2,3,4]
x[3:] # [3,4,5,6,7,8]
x[:-1] # [0,1,2,3,4,5,6,7]

• 按照一定步长访问数据
  List[i:j:n] n为步长
  x = [1,2,3,4,5,6,7,8]
x[0:5:2] 结果为[1,3,5,7]
x[::2] 结果为[0,2,4,6]

• 基本的内置全局函数
  x = list(range(10))
len(x) = 10
max(x) = 9
min(x) = 0
sum(x) = 45
x.index("4") 确定4这个值的下标值
  y = [3,3,4,5,5,6,6,6,7,8,9]
x.count("5") = 2 计算出次数