Loop in dictionary definition

New to Julia
1

Hello,
I’m using a library that uses a dictionary to set variables along points, like so:

bla = Dict(
    1 => foo,
    2 => bar
)

I want to create that dictionary over a large number of points and that number is not constant. Something like:

bla = Dict(
    for i in 1:N
        i => foo[i],
    end
)

How can I achieve this?
Thanks a lot!

2

You can use a comprehension for this::

julia> N = 5;

julia> foo = rand(N);

julia> bla = Dict(i => foo[i] for i in 1:N)
Dict{Int64, Float64} with 5 entries:
  5 => 0.825488
  4 => 0.308265
  2 => 0.932313
  3 => 0.495245
  1 => 0.490559
1 Like
3

Oh, that’s great, thanks!
How do I combine that with a defined entry? I never worked with Dictionaries before. Can I add a new point (say point 6) after bla = Dict(i => foo[i] for i in 1:N)?
Something like:

bla = Dict(i => foo[i] for i in 1:N, 6=>0.2)

Thanks!

4

Just figured out the merge command. So if that’s the way to go, I’m happy. Thanks again!

5

Yup, merge will certainly work. On the other hand, you might also consider just using a loop–loops are fast in Julia, and often the easiest way to do things:

julia> d = Dict{Int, Float64}()
Dict{Int64, Float64}()

julia> for i in 1:N
         d[i] = foo[i]
       end

julia> d[6] = 0.2
0.2

julia> d
Dict{Int64, Float64} with 6 entries:
  5 => 0.825488
  4 => 0.308265
  6 => 0.2
  2 => 0.932313
  3 => 0.495245
  1 => 0.490559
6

Ah, that is also a neat way to do it. Thanks!