当您不知道序列长度时，Python 中的多重解包赋值 [英] Multiple Unpacking Assignment in Python when you don't know the sequence length

问题描述

多次拆包赋值的教科书例子是这样的:

The textbook examples of multiple unpacking assignment are something like:

import numpy as NP
M = NP.arange(5)
a, b, c, d, e = M
# so of course, a = 0, b = 1, etc.

M = NP.arange(20).reshape(5, 4)     # numpy 5x4 array
a, b, c, d, e = M
# here, a = M[0,:], b = M[1,:], etc. (ie, a single row of M is assigned each to a through e)

(我的问题不是特定于 numpy 的.确实，我更喜欢纯 Python 解决方案.)

(My question is not numpy specific. Indeed, I would prefer a pure Python solution.)

对于我现在正在查看的一段代码，我看到在这个简单的场景中存在两个复杂情况:

For the piece of code I'm looking at now, I see two complications on that straightforward scenario:

• 我通常不知道M的形状；和

• I usually won't know the shape of M; and

我想解压一定数量的项目(绝对少于所有项目)，以及我想把剩下的变成一个单容器

I want to unpack a certain number of items (definitely less than all items), and I want to put the remainder into a single container

那么回到上面的 5x4 数组，我非常想做的是将 M 的前三行分别分配给 a、b 和 c(完全如上)，而 其余的行(我不知道会有多少，只是一些正整数)到单个容器中，all_the_rest = [].

So back to the 5x4 array above, what I would very much like to do is assign the first three rows of M to a, b, and c respectively (exactly as above), and the rest of the rows (I have no idea how many there will be, just some positive integer) to a single container, all_the_rest = [].

推荐答案

Python 3.x 可以轻松做到这一点:

Python 3.x can do this easily:

a, b, *c = someseq

Python 2.x 需要做更多的工作:

Python 2.x needs a bit more work:

(a, b), c = someseq[:2], someseq[2:]

这篇关于当您不知道序列长度时，Python 中的多重解包赋值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！