Library that converts a Python output string to an Elisp data structure?

Question

Say that I evaluate the following Python code:

import inspect
import scipy.ndimage.filters

list (inspect.getargspec (scipy.ndimage.filters.gaussian_filter1d))
# => [['input', 'sigma', 'axis', 'order', 'output', 'mode', 'cval'],
#      None, None, (-1, 0, None, 'reflect', 0.0)]

I'd like to transform the output string, which is simply Python's print output, to an Elisp data structure. So I need a function foo that does this:

(foo "[['input', 'sigma', 'axis', 'order', 'output', 'mode', 'cval'], None, None, (-1, 0, None, 'reflect', 0.0)]")
;; =>
;; (("input"
;;   "sigma"
;;   "axis"
;;   "order"
;;   "output"
;;   "mode"
;;   "cval")
;;  nil
;;  nil
;;  (-1 0 nil "reflect" 0.0))

While it's not hard to write a version of foo that works for this specific instance, I wonder if there's a library that does this in a generic way, i.e. it is able to handle any complex Python structure.

Answer 1

Use JSON, not Python syntax

What you are looking for is json.el which is a part of Emacs.

Note that it will not read Python format OOTB; there are at least 3 problems:

1. 'foo' is not recognized as a string
2. keywords true/false/null are recognized instead of True/False/None
3. tuples (1,"bar") are not recognized

Full solution using json.dumps in Python

Python can easily print its data structures as JSON:

(require 'json)
(require 'python)
(json-read-from-string
 (substring
  (python-shell-send-string-no-output
   "import inspect, json; json.dumps (inspect.getargspec (json.dumps))"
   (run-python))
  1 -1))
==>
[["obj" "skipkeys" "ensure_ascii" "check_circular" "allow_nan"
  "cls" "indent" "separators" "encoding" "default" "sort_keys"]
 nil "kw" [:json-false t t t nil nil nil "utf-8" nil :json-false]]