NamedTuples are, as their name suggests, named Tuples. That is, they're a tuple-like collection of values, where each entry has a unique name, represented as a Symbol. Like Tuples, NamedTuples are immutable; neither the names nor the values can be modified in place after construction.

Accessing the value associated with a name in a named tuple can be done using field access syntax, e.g. x.a, or using getindex, e.g. x[:a]. A tuple of the names can be obtained using keys, and a tuple of the values can be obtained using values.


Iteration over NamedTuples produces the values without the names. (See example below.) To iterate over the name-value pairs, use the pairs function.

The @NamedTuple macro can be used for conveniently declaring NamedTuple types.


julia> x = (a=1, b=2)
(a = 1, b = 2)

julia> x.a

julia> x[:a]

julia> keys(x)
(:a, :b)

julia> values(x)
(1, 2)

julia> collect(x)
2-element Vector{Int64}:

julia> collect(pairs(x))
2-element Vector{Pair{Symbol, Int64}}:
 :a => 1
 :b => 2

In a similar fashion as to how one can define keyword arguments programmatically, a named tuple can be created by giving a pair name::Symbol => value or splatting an iterator yielding such pairs after a semicolon inside a tuple literal:

julia> (; :a => 1)
(a = 1,)

julia> keys = (:a, :b, :c); values = (1, 2, 3);

julia> (; zip(keys, values)...)
(a = 1, b = 2, c = 3)

As in keyword arguments, identifiers and dot expressions imply names:

julia> x = 0

julia> t = (; x)
(x = 0,)

julia> (; t.x)
(x = 0,)
Julia 1.5

Implicit names from identifiers and dot expressions are available as of Julia 1.5.