就是遍历
lst = [1,2,3,4,5] for i in lst: print(i)
意思就是遍历 lst , 依次返回 1,2,3,4,5
for i in 也可以嵌套,你贴的图,就是2层嵌套
>>> lst = ['abc','123'] >>> [i for j in lst for i in j] ['a', 'b', 'c', '1', '2', '3']