How to Read and Write JSON files in julia

write_read_json.jl

import JSON
###################
### Write data ####
###################
# dictionary to write
dict1 = Dict("param1" => 1, "param2" => 2,
            "dict" => Dict("d1"=>1.,"d2"=>1.,"d3"=>1.))
            
# pass data as a json string (how it shall be displayed in a file)
stringdata = JSON.json(dict1)

# write the file with the stringdata variable information
open("write_read.json", "w") do f
        write(f, stringdata)
     end

###################
### Read data #####
###################
# create variable to write the information
dict2 = Dict()
open("write_read.json", "r") do f
    global dict2
    dicttxt = readall(f)  # file information to string
    dict2=JSON.parse(dicttxt)  # parse and transform data
end

# print both dictionaries
println(dict1)
println(dict2)

The 'readall' call fails with 'ERROR: UndefVarError: readall not defined'. If 'readall' is replaced by 'readstring', it works fine.

Very helpfull. Thanks for sharing.

How to get the value, because is showing in my console: Dict{Any,Any}()

I think the readall(f) call was supposed to be JSON.readall

# create variable to write the information
dict2 = Dict()
open("write_read.json", "r") do f
    global dict2
    dicttxt = read(f,String)  # file information to string
    dict2=JSON.parse(dicttxt)  # parse and transform data
end

and

# create variable to write the information
dict2 = Dict()
open("write_read.json", "r") do f
    global dict2
    dict2=JSON.parse(f)  # parse and transform data
end

worked!

It seems the name of text-read function has been changed at least twice: readall -> readstring -> read
JuliaLang/julia#14660
JuliaLang/julia#22864

Julia v1.5 update: for reading data I use

stringdata=join(readlines("/path/data.json"))
dict=JSON.parse(stringdata)

Using Julia v1.5 and the Pipe module you can read the json file to a dict in one line:

dict = @pipe "write_read.json" |> open |> read |> String |> JSON.parse

Using Julia v1.6, I was able to read the json file in a very simple way.

dict = "write_read.json" |> open |> JSON.parse
OR
dict = JSON.parse(open("write_read.json"))

I think JSON.parsefile("filename.json") is the right way to do this now?