Format content from JSON file?

Questions / Help
1

I want to get rid of the strings "" being displayed from the Enum.random()
like: " \"Dislike_YouTube\",\n" => Dislike_YouTube

I tried to do Poison.decode!() but its erroring:

File.stream!("names.json")
|> Enum.random()
|> Poison.decode!()

** (Poison.ParseError) unexpected token at position 21: ,

2

Picking random line from JSON file do not guarantee that the returned string will be proper JSON string. First decode, then pick random (if you can).

3

ye it tried to move the decode above the random actually but then got:

** (ArgumentError) errors were found at the given arguments:

  * 1st argument: not an iodata term

    :erlang.iolist_to_binary(%File.Stream{line_or_bytes: :line, modes: [:raw, :read_ahead, :binary], path: "names.json", raw: true})
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4

decode! is not happy with File.Stream.t as input. Try File.read! or more generally, try reading the docs.

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5

If you have a huge JSON file then you may consider using jaxon library instead.

Take a look at example from it’s readme file:

"large_file.json"
|> File.stream!()
|> Jaxon.Stream.from_enumerable()
|> Jaxon.Stream.query([:root, "users", :all, "metadata"])
|> Stream.map(&(&1["username"],",",&1["email"],"\n"))
|> Stream.into(File.stream!("large_file.csv"))
|> Stream.run()
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6

well its around 5k lines and what I want to do is to return a random name like
Mad_Player but I always get "Mad_Player" back, is that a problem?

7

Here is example names.json file content:

[
  "First",
  "Second",
  "Third"
]

and here is a code:

"names.json"
|> File.stream!()
|> Jaxon.Stream.from_enumerable()
|> Jaxon.Stream.query([:root, :all])
|> Enum.random()

As long as it’s a valid json file the format does not matter. Each name can be in separate line as well as in one line.

8

What’s the output of that?

9

A random Elixir string like "First".

10

I’d not recommend this solution for a beginner, rather just

"names.json"
|> File.read!()
|> Jason.decode!()
|> Enum.random()
1 Like
11

Thanks

12

If I do Jason.decode(File.read('names.json'), I get that error
1st argument: not an iodata term. The json is in this format
{:ok, "{\n \"key\": \"value\"\n}"} with a weird :ok that I don’t know how to deal with.

But your syntax works. I don’t get it

13

you forgot the !. Without it those functions return an ok-tuple, with they raise.

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