它们是可以轻松创建字典和列表的语法结构。

由输出项，列表项，过滤项组成，过滤项为bool值可省略

[expr for itm in collection if condition] 列表常规推导

lst = [11,22,33,44]result = [i for i in range(10) if i%2==0]print(result)#注意是==,否则报错lst = [11,22,33,44]result = [i for i in lst if i%2==0]print(result)

zero = [0,-1,5,3,-9,-3,6,2]zero_list = [x**2 for x in zero if x >0]print(zero_list)

 

(expr for itm in collection if condition) 列表迭代推导,

也可以说是生成器表达式,这个给出的结果是一个生成器

lst = [11,22,33,44]result = (i for i in lst if i%2==0)print(result)

       
         at 0x0000000004DA9F68>
       

{key: value for (key, value) in iterable}字典推导

lst=[1,2,3,4,5]res={i:'python'+str(i)+'期' for i in lst if i>3}print(res)

打印结果:{4: 'python4期', 5: 'python5期'}

{expr for itm in collection if condition} 集合推导

 

lst=[1,2,3,4,5,5,2,3]res={i for i in lst if i>0}print(res)# 结果直接过滤重复元素

{1, 2, 3, 4, 5}