How do I import a Dataset that contains lists?

Question

The very first example in the Dataset documentation is the following:

dataset = Dataset[{
<|"a" -> 1, "b" -> "x", "c" -> {1}|>,
<|"a" -> 2, "b" -> "y", "c" -> {2, 3}|>,
<|"a" -> 3, "b" -> "z", "c" -> {3}|>,
<|"a" -> 4, "b" -> "x", "c" -> {4, 5}|>,
<|"a" -> 5, "b" -> "y", "c" -> {5, 6, 7}|>,
<|"a" -> 6, "b" -> "z", "c" -> {}|>}]

The third column of this dataset contains Lists. I would like to create a file that I can read (e.g. using SemanticImport) and that will parsed into this format.

An example for a String that does not work:

datatest = SemanticImportString["a\tb\tc\1\tx\t{1}\n"]

Here the column labeled "c" becomes the String "{1}".

Similarly,

datatest = SemanticImportString["a\tb\tc\n1\tx\t{1}\n", {"String", "String", "List"}]

puts the String "{1}" into a List: {"{1}"}.

Since the Dataset format is touted as a way to work with hierarchical data sets I assume there must be some convenient way to actually read in a hierarchical data set? Many thanks!

Answer 1

From what I can tell you want {1} in your string to be read as a Mathematica expression, i.e. read as a List. I believe you may therefore use the type "Expression":

SemanticImportString["a\tb\tc\n1\tx\t{1}\n", {"String", "String", "Expression"}]