# Syntax for extracting keys from vector of pairs?
**URL:** https://discourse.julialang.org/t/syntax-for-extracting-keys-from-vector-of-pairs/130063
**Category:** General Usage
**Tags:** arrays
**Created:** [June 20, 2025, 2:27pm UTC](https://discourse.julialang.org/t/syntax-for-extracting-keys-from-vector-of-pairs/130063 "2025-06-20T14:27:46Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@g2g](https://discourse.julialang.org/u/g2g)
#### Post date: [June 20, 2025, 2:27pm UTC](https://discourse.julialang.org/t/syntax-for-extracting-keys-from-vector-of-pairs/130063/1 "2025-06-20T14:27:46Z")
```julia
julia> X
3-element Vector{Pair{String, Any}}:
"water" => [1 2]
"coffee" => [3 4 5]
"tea" => [6 7 8 9]
```
To extract the keys from X, the current syntax is first.(X). However, given that the syntax for extracting a column from a single pair uses indexing like this
```julia
julia> X[2][1]
"coffee"
julia> X[2][2]
1×3 Matrix{Int64}:
3 4 5
```
wouldn’t a more “regular form” of the syntax to extract all keys be X.[1] instead of first.(X)?
---
### Author:  [@nilshg](https://discourse.julialang.org/u/nilshg)
#### Post date: [June 20, 2025, 2:38pm UTC](https://discourse.julialang.org/t/syntax-for-extracting-keys-from-vector-of-pairs/130063/2 "2025-06-20T14:38:58Z")
See this discussion and issues linked therein:
>
>
> I have an array \`x::Array{ImmutableArray.Vector2}\`.
>
> It would be cool to be ab…le to broadcast indexing as is done with functions.
> e.g.
> \`\`\`x.\[1\]\`\`\`,
> which would return the first element of each \`Vector2\` in my array.
>
> This is currently achievable with \`getindex.(x,1)\` or in the case of a range of indices
> \`getindex.(x,\[range\])\`.
---
### Author:  [@Nathan\_Boyer](https://discourse.julialang.org/u/Nathan_Boyer)
#### Post date: [June 20, 2025, 5:02pm UTC](https://discourse.julialang.org/t/syntax-for-extracting-keys-from-vector-of-pairs/130063/3 "2025-06-20T17:02:55Z")
You can use a general index with `getindex`.
```julia
julia> getindex.(X, 1)
3-element Vector{String}:
"water"
"coffee"
"tea"
julia> getindex.(X, 2)
3-element Vector{Matrix{Int64}}:
[1 2]
[3 4 5]
[6 7 8 9]
```
If you use a dictionary instead of vector of pairs, you can get the keys with the `keys` function.
```julia
julia> using OrderedCollections
julia> Xdict = OrderedDict(X)
OrderedDict{String, Matrix{Int64}} with 3 entries:
"water" => [1 2]
"coffee" => [3 4 5]
"tea" => [6 7 8 9]
julia> keys(Xdict)
KeySet for a OrderedDict{String, Matrix{Int64}} with 3 entries. Keys:
"water"
"coffee"
"tea"
julia> values(Xdict)
ValueIterator for a OrderedDict{String, Matrix{Int64}} with 3 entries. Values:
[1 2]
[3 4 5]
[6 7 8 9]
```
---
### Author:  [@mbauman](https://discourse.julialang.org/u/mbauman)
#### Post date: [June 20, 2025, 5:24pm UTC](https://discourse.julialang.org/t/syntax-for-extracting-keys-from-vector-of-pairs/130063/4 "2025-06-20T17:24:05Z")
As of yesterday, Julia v1.13 has a new `Iterators.nth` that generalizes `first` and `last`. And it has a “functor” like form that you can broadcast:
```julia-repl
julia> X = [
"water" => [1 2]
"coffee" => [3 4 5]
"tea" => [6 7 8 9]];
julia> Iterators.nth(1).(X)
3-element Vector{String}:
"water"
"coffee"
"tea"
julia> Iterators.nth(2).(X)
3-element Vector{Matrix{Int64}}:
[1 2]
[3 4 5]
[6 7 8 9]
```
Yeah, I know it’s not as “pretty” as an indexing expression. But you can now easily make ordinal numbers work (albeit with parentheses or piping; the precedence of the function call “wins” over the juxtaposition):
```Julia-repl
julia> struct OrdinalIndicator; end
julia> Base.:*(i::Integer, ::OrdinalIndicator) = Iterators.nth(i)
julia> const ᵗʰ = const ʳᵈ = const ⁿᵈ = const ˢᵗ = OrdinalIndicator()
OrdinalIndicator()
julia> (1ˢᵗ).(X)
3-element Vector{String}:
"water"
"coffee"
"tea"
julia> X .|> 2ⁿᵈ
3-element Vector{Matrix{Int64}}:
[1 2]
[3 4 5]
[6 7 8 9]
```
(and yes, this is mostly a joke)
---
### Author:  [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)
#### Post date: [June 20, 2025, 10:59pm UTC](https://discourse.julialang.org/t/syntax-for-extracting-keys-from-vector-of-pairs/130063/5 "2025-06-20T22:59:14Z")
> [@mbauman](#):
>
> this is mostly a joke
But a nice joke.
Another variant of it:
```julia
_¹ˢᵗ = Iterators.nth(1)
_²ⁿᵈ = Iterators.nth(2)
_³ʳᵈ = Iterators.nth(3)
_⁴ᵗʰ = Iterators.nth(4)
_⁵ᵗʰ = Iterators.nth(5)
# ...
```