NamedTuple, how to assign values?

New to Julia
1

Hello!

Suppose I have a line as such:

varNames = NamedTuple{(:key,:offset,:type,:ncol), Tuple{String,Int,DataType,Int}}

The typeof this is:

typeof(varNames)
DataType

Then my question is; how do I insert values into, i.e. construct a NamedTuple based on this data type?

Kind regards

2

I don’t know why you want to do this, you’re probably looking for a struct.

That said,

julia> varNames(("hi",3,String,4))
(key = "hi", offset = 3, type = String, ncol = 4)
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3

Thanks!

I ended up doing it differently this time as you hinted at (dict, instead of struct), but knowledge is power, so thanks for sharing the correct way to do it! :blush:

Kind regards

4

That’s probably fine. Just wanted to point out that there are many advantages to a struct over a Dict for something like this, performance wise.

struct VarNames
    key::String
    offset::Int
    type::DataType
    ncol::Int
end

It gives you dispatch, clearer contract and more efficient storage than a Dict{Symbol, Any}. If you’re willing to void the dispatch you could have also just used a NamedTuple like you first suggested, but without the intermediate type alias:

x = (key="hi", offset=3, type=String, ncol=4)

But if it works it works.

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5

You can’t insert values in a NamedTuple (or a Tuple for what does it matter), as these are immutable types, after they have been created you can’t modify them (you can still modify -but not reassign - mutable elements of it)

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