In Julia, how to merge a dictionary?

You can use merge. If the Dicts have elements with the same key, the value for that key will be of the last Dict listed. If you want to combine the elements of the Dicts that have the same key, you can use merge(combine, collection, others...). combine is a function that receive two values and return a value.

Example of the docs:

julia> a = Dict("foo" => 0.0, "bar" => 42.0)
Dict{String,Float64} with 2 entries:
  "bar" => 42.0
  "foo" => 0.0

julia> b = Dict("baz" => 17, "bar" => 4711)
Dict{String,Int64} with 2 entries:
  "bar" => 4711
  "baz" => 17

julia> merge(+, a, b)
Dict{String,Float64} with 3 entries:
  "bar" => 4753.0
  "baz" => 17.0
  "foo" => 0.0

https://docs.julialang.org/en/latest/base/collections/#Base.merge

merge(collection, others...)

Construct a merged collection from the given collections. If necessary, the types of the resulting collection will be promoted to accommodate the types of the merged collections. If the same key is present in another collection, the value for that key will be the value it has in the last collection listed.

julia> merge(dict1,dict2)
    Dict{ASCIIString,Int64} with 6 entries:
      "f" => 6
      "c" => 3
      "e" => 5
      "b" => 2
      "a" => 1
      "d" => 4

merge!(collection, others...)
Update collection with pairs from the other collections.

julia> merge!(dict1,dict2)
Dict{ASCIIString,Int64} with 6 entries:
  "f" => 6
  "c" => 3
  "e" => 5
  "b" => 2
  "a" => 1
  "d" => 4

julia> dict1
Dict{ASCIIString,Int64} with 6 entries:
  "f" => 6
  "c" => 3
  "e" => 5
  "b" => 2
  "a" => 1
  "d" => 4