Question

我将如何进行以下操作？

class a:
    def get(self):
        return (1, 2)

i = a() #this is variable that i wont have access directly and should be accessed only from list P below
P = [i, i, i, i]
Q = [P, P, P, P]

我想要的是

L = [list of all i.get() results iterating through Q and P]

例如

L = [px.get() for px in P for P in Q] # I want something like this

即

L = [(1, 2), (1, 2), (1, 2), (1, 2), (1, 2), (1, 2), (1, 2), (1, 2), (1, 2), (1, 2), (1, 2), (1, 2), (1, 2), (1, 2), (1, 2), (1, 2)]

Answer 1

使用列表理解：

L = [i.get() for P in Q for i in P]

这会为您提供[Q[0][0].get(), Q[0][1].get(), ..., Q[-1][-2].get(), Q[-1][-1].get()]

双循环就像是列表推导之外的嵌套for循环，上面相当于：

L = []
for P in Q:
    for i in P:
        L.append(i.get())

列表推导遵循相同的循环顺序，嵌套转换为从左到右列出的循环。

Answer 2

可以使用Python中的*运算符（即multiplying a list）复制列表：

>>> [i.get()] * (len(P) + len(Q))
[(1,2), (1,2), (1,2), (1,2), (1,2), (1,2), (1,2), (1,2)]

迭代python 2.7中的列表

2 个答案: