Dictionary Initialization and Usage

General Usage
1

I started with Julia today and was experimenting with Dictionary feature. The following is the code I wrote when I faced the error. Could anyone point out as to why such error is occuring and why such usage is wrong?

error_1
error_11134×541 47.2 KB

Any help would be appreciated!

3

Maybe Julia thinks it is inconceivable that Freiburg is third??

The actual answer is:

julia> x = Dict{String, Int64}
Dict{String, Int64}

julia> typeof(x) # x is not a Dict!
DataType

you have not instantiated a Dictionary, but rather assigned the value Dict{String, Int64}, which is a type, to the binding bundesliga_table_position.

The error is telling you that you cannot add an entry to a DataType. To instantiate an object of a type, use parentheses:

julia> x = Dict{String, Int64}()
Dict{String, Int64}()

julia> typeof(x) # x is a Dict now!
Dict{String, Int64}

julia> x["a"] = 1
1

julia> x
Dict{String, Int64} with 1 entry:
  "a" => 1
2 Likes
4

Although inconceivable for sure :wink: your answer is spot on. I didn’t think this was even possible!
Thank you for your crisp and prompt answer. Thanks for the help!

5

No problem. One additional complication that I missed is that your first line also made bundesliga_table_position and alias for Dict{String, Int64} which can therefore be used to construct a dictionary. So you’ve essentially created a less flexible Dict constructor:

julia> my_alias = Dict{String, Int64}
Dict{String, Int64}

julia> Dict("a" => 1, "b" => 2)
Dict{String, Int64} with 2 entries:
  "b" => 2
  "a" => 1

julia> my_alias("a" => 1, "b" => 2) # my_alias can now create new Dicts
Dict{String, Int64} with 2 entries:
  "b" => 2
  "a" => 1

julia> my_alias("a" => "b", "b" => "c") # But only String => Int Dicts
ERROR: MethodError: Cannot `convert` an object of type String to an object of type Int64

julia> Dict("a" => "b", "b" => "c") # Unlike the actual Dict constructor
Dict{String, String} with 2 entries:
  "b" => "c"
  "a" => "b"
1 Like
6

Ohh yes. That makes sense. :+1: