juliadefaultdict对每个键使用相同的值(数组)

x -> Int64 ,那么这就没有意义了:initilizer不需要参数,它应该返回一个值,而不是一个类型。你可能想用的是 () -> Int64[] :

julia> genome = DefaultDict{Tuple{String, String}, Array{Int64, 1}}(() -> Int64[])
DefaultDict{Tuple{String,String},Array{Int64,1},getfield(Main, Symbol("##7#8"))} with 0 entries

julia> genome["a", "b"]
0-element Array{Int64,1}

julia> push!(genome["a", "c"], 5)
1-element Array{Int64,1}:
 5

julia> genome
DefaultDict{Tuple{String,String},Array{Int64,1},getfield(Main, Symbol("##7#8"))} with 2 entries:
  ("a", "c") => [5]
  ("a", "b") => Int64[]

julia> push!(genome["a", "b"], 4)
1-element Array{Int64,1}:
 4

julia> genome
DefaultDict{Tuple{String,String},Array{Int64,1},getfield(Main, Symbol("##7#8"))} with 2 entries:
  ("a", "c") => [5]
  ("a", "b") => [4]

如果要基于尝试过的键创建默认值,可以使用 passkey = true 以及一个以键为参数的初始化函数;看见 the docs 所有选项。

get!(collection, key, default)

genome = Dict{Tuple{String, String}, Array{Int64, 1}}()
push!(get!(genome, ("chr1", "+"), Int64[]), 5)
# 1-element Array{Int64,1}:
# 5

push!(get!(genome, ("chrX", "-"), Int64[]), 10)
# 1-element Array{Int64,1}:
# 10