008 列表与生成式

例1 创建列表

>>> a = [1, 2, 3]
>>> b = [i for i in a]
>>> b
[1, 2, 3]
>>> id(a)
2119645020288
>>> id(b)
2119640566656

例2 过滤列表

>>> a = list(range(10))
>>> b = [i for i in a if i % 2 == 0]
>>> b
[0, 2, 4, 6, 8]
>>> 

例3 嵌套

>>> a = [1, 2, 3]
>>> b = [100, 200, 300]
>>> c = [m + n for m in a for n in b]
>>> c
[101, 201, 301, 102, 202, 302, 103, 203, 303]
>>> 
>>> d = [m + n for m in a for n in b if m + n < 300]
>>> d
[101, 201, 102, 202, 103, 203]
>>>