Putting quotes around array, e.g. "[1,2,3,4]"

Questions / Help
1

Hi:

I need to pass an array to a Python script through a Port where the values in array are quoted. So, how do I convert

[1,2,3,4]

to

"[1,2,3,4]"

Thanks!

gani-

2

Perhaps this?

iex> inspect [1,2,3,4]
"[1, 2, 3, 4]"
3 Likes
3

Yes, that works! I just found another way in the documentation which is more convoluted but works just the same.

p1 = press = 0..10 |> Enum.to_list()
p2= Macro.to_string(quote do: unquote(p1))
#=> "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]"
4

You could also use Jason.encode!

iex(8)> Jason.encode!([1, 2, 3, 4])
"[1,2,3,4]"

It might also help with code readability.

You will need to add it to your mix.exs file if it isn’t already included

defp deps do
  [
    {:jason, "~> 1.2"}
  ]
end
1 Like
5

I’d strongly suggest using a data format known to both the elixir and the python side – like json. Inspect converts terms to a string representation in elixir syntax. This is not meant to work with python (even if it might in some places).

9 Likes
6

Thanks!
gani-

7

I’ve had great success using this module with python ports: GitHub - okeuday/erlang_py: Erlang External Term Format for Python

8

Here’s another one:

iex> "[#{Enum.join([1,2,3,4], ",")}]"
"[1,2,3,4]

Or you could pass it as an iolist:

iex> IO.puts ["[", Enum.join([1,2,3,4], ","), "]"]
[1,2,3,4]

Actually, I’m not sure now if you actually want to include the " or whether you just wanted a string representing an array.

2 Likes
9

Until you do:

iex> inspect [100, 101, 102]
"'def'"

:wink:

Personally, I’d use one of the more formal, established approaches for coaxing data across the Elixir/Python divide, such as JSON or Erlang_py discussed above. The corner cases have been sorted so you don’t have to.

FWIW - You can fix the inspect approach with the charlists option:

iex(5)> inspect [100, 101, 102], charlists: :as_lists
"[100, 101, 102]"
6 Likes
10

Thank you!