从列表中获取嵌套元素 [英] Getting nested elements from a list

问题描述

我正在尝试从列表中获取嵌套元素.我可以使用unlist(pull_lists[[i]]$content[[n]]['sha'])提取元素，但是，似乎无法将它们插入嵌套列表中.我已根据要点提取了列表的单个元素，从而在下面创建了可重现的示例.这是我到目前为止的内容:

I am trying to get nested elements from a list. I can extract the elements using: unlist(pull_lists[[i]]$content[[n]]['sha']), however, it seems that I cannot insert them in a nested list. I have extracted a single element of the list in a gist, which creates the reproducible example below. Here is what I have so far:

library("devtools")
pull_lists <- list(source_gist("669dfeccad88cd4348f7"))

sha_list <- list()
for (i in length(pull_lists)){
  for (n in length(pull_lists[[i]]$content)){
  sha_list[i][n] <- unlist(pull_lists[[i]]$content[[n]]['sha'])
  }
}

如何以嵌套方式插入元素?

How can I insert the elements in a nested fashion?

推荐答案

下载内容时，我得到的结构要比您复杂得多.对我来说，它不是pull_lists[[i]]$content，它是pull_lists[[i]]$value$content[[1 or 2]]$parents$sha.没什么可填充的原因是因为那里没有可填充的东西(即n = 0).

When I download the content, I get a much more complicated structure than you do. For me, it's not pull_lists[[i]]$content, it's pull_lists[[i]]$value$content[[1 or 2]]$parents$sha. The reason nothing is populating is because there is nothing there to populate (ie, n = 0).

我以前不得不处理类似的数据结构.我发现，取消列出后搜索命名结构要比找出正确的子集顺序容易得多.

I've had to deal with similar data structures before. What I found was that it's much easier to search the naming structure after unlisting rather than to figure out the correct sequence of subsets.

这是一个例子:

sha_locations <- grep("sha$",names(unlist(pull_list[[1]])))
unlist(pull_list[[1]])[sha_locations] 

稍微清洁一下for循环，这看起来像:

Cleaning the for loop a bit, this would look like:

sha_list <- lapply(
   pull_list, 
   function(x) unlist(x)[grep("sha$",names(unlist(x)))]
)

由于存在多个SHA，并且该问题仅要求在特定位置提供SHA，因此您需要提取这些SHA:

Since there are multiple SHAs, and the question only asks for the SHAs at specific positions, you need to extract those SHAs:

sha_list <- sha_list[[1]][attr(sha_list[[1]], "names")=="value.content.sha"]

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