在Julia语言中，向字典的现有键添加键值对。

Question

我正在使用Julia 1.63并尝试在循环中创建一个字典。 我可以从以下字典开始。

dict = Dict("A_1" => 1, "B_1" => 2, "X" => "A_1" => 1)
Dict{String, Any} with 3 entries:
  "X"   => "A_1"=>1
  "B_1" => 2
  "A_1" => 1

现在我想将键“X”添加键值对“B_2” => 2。

我尝试了以下内容：

push!(dict["X"],Dict("B_2" => 2))
ERROR: MethodError: no method matching push!(::Pair{String, Int64}, ::Dict{String, Int64})
Closest candidates are:
  push!(::Any, ::Any, ::Any) at abstractarray.jl:2387
  push!(::Any, ::Any, ::Any, ::Any...) at abstractarray.jl:2388
  push!(::AbstractChannel, ::Any) at channels.jl:10

push!(dict["X"],"B_2" => 2)
ERROR: MethodError: no method matching push!(::Pair{String, Int64}, ::Pair{String, Int64})
Closest candidates are:
  push!(::Any, ::Any, ::Any) at abstractarray.jl:2387
  push!(::Any, ::Any, ::Any, ::Any...) at abstractarray.jl:2388
  push!(::AbstractChannel, ::Any) at channels.jl:10

我对此感到疑惑的是，这在字典的上层 工作。

push!(dict,"B_2" => 2)
Dict{String, Any} with 4 entries:
  "B_2" => 2
  "X"   => "A_1"=>1
  "B_1" => 2
  "A_1" => 1

我是否忽略了什么显而易见的问题？感谢您的帮助。

- lambcount

Answer 1

问题在于 "X" 的值不是一个 Dict，而是一个 Pair。如果您想要为一个键分配多个 Pair，应该使用 Dict。您需要相应地初始化它。

julia> dict = Dict("A_1" => 1, "B_1" => 2, "X" => Dict("A_1" => 1))
Dict{String, Any} with 3 entries:
  "X"   => Dict("A_1"=>1)
  "B_1" => 2
  "A_1" => 1
julia> push!(dict["X"],"B_2" => 2) 
Dict{String, Int64} with 2 entries:
  "B_2" => 2
  "A_1" => 1
julia> dict
Dict{String, Any} with 3 entries:
  "X"   => Dict("B_2"=>2, "A_1"=>1)
  "B_1" => 2
  "A_1" => 1

- ginkul