如何向现有字典添加新的键值对？

Question

我有一些已经存在的字典。我想添加一个新的键值对，但我不想从头开始创建一个新字典。

如何向 Julia 中的现有字典添加新的键值对？

Answer 1

Julia 使用通用dict[key] = value语法来设置键值对：

julia> dict = Dict(1 => "one")
Dict{Int64,String} with 1 entry:
  1 => "one"

julia> dict[2] = "two"
"two"

julia> dict
Dict{Int64,String} with 2 entries:
  2 => "two"
  1 => "one"

如果键已经存在，相同的语法将覆盖键值对：

julia> dict
Dict{Int64,String} with 2 entries:
  2 => "two"
  1 => "one"

julia> dict[1] = "foo"
"foo"

julia> dict
Dict{Int64,String} with 2 entries:
  2 => "two"
  1 => "foo"

dict[key] = value是setindex!调用的语法。虽然不常见，但你可以setindex!直接调用：

julia> dict = Dict(1 => "one")
Dict{Int64,String} with 1 entry:
  1 => "one"

julia> setindex!(dict, "two", 2)
Dict{Int64,String} with 2 entries:
  2 => "two"
  1 => "one"