Example:
I save data to a MX file, like:
a=Range[100]; b=Range[1000]; Export["data.mx", {a,b}, "MX"]; Can I after importing the data:
data = Import["data.mx", "MX"]; also retrieve the names of the variables a,b?
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2 
- 3$\begingroup$ related: DumpSave for the forgetful $\endgroup$Kuba– Kuba2017-05-10 13:20:34 +00:00Commented May 10, 2017 at 13:20
- $\begingroup$ great link, thank you. $\endgroup$lio– lio2017-05-10 13:24:22 +00:00Commented May 10, 2017 at 13:24
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1 Answer
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4 No, because those names were never saved into the file.
If you want the names saved too, you can use DumpSave instead of Export for saving, and Get instead of Import for loading. In this case, a and b will be overwritten upon Get. I do not like this method because I need to remember those names, and because I consider overwriting dangerous.
Personally I would export an association instead of a list:
<|"a" -> a, "b" -> b|> This way I can make the structure of the data self-explanatory.
- $\begingroup$ Could I do this:
Export["data.mx", <|"a" -> a, "b" -> b|>, "MX"];? and reading would be:data = Import["data.mx"]? After reading how do I assigna=...andb=...? $\endgroup$lio– lio2017-05-10 13:57:39 +00:00Commented May 10, 2017 at 13:57 - $\begingroup$ @lio Yes, that is what I meant I would do. But the whole reason why I suggested associations was to avoid assigning. If you want to assign
aandbafter reading, then I suggest you useDumpSave/Get. $\endgroup$Szabolcs– Szabolcs2017-05-10 13:59:42 +00:00Commented May 10, 2017 at 13:59 - $\begingroup$ Thank you for the explanation ... $\endgroup$lio– lio2017-05-10 19:36:14 +00:00Commented May 10, 2017 at 19:36
- $\begingroup$ @lio To be fair, you can set values based on an association, but it requires something a bit more advanced:
setName[name_String, value_] := ToExpression[name, InputForm, Function[s, s = value, HoldAll]]NowsetName["a", 1]sets the value ofato1. So you can doKeyValueMap[setName, <|"a" -> 1, "b" -> 2|>]to setato1andbto2. $\endgroup$Szabolcs– Szabolcs2017-05-10 19:40:47 +00:00Commented May 10, 2017 at 19:40