Python port of neatjson gem from Ruby

neatjson.py

import re
import json
import inspect
from collections import OrderedDict as odict

def neatify(obj,**opts):
  """
  Generate the JSON string representation for an object,
  with a variety of formatting options.

  original author Gavin Kistner <!@phrogz.net>
  ported by Rei_Fan49

  obj [Object] the object to serialize
  opts [Dict] the formatting options
  opts [Integer] wrap        (80)    The maximum line width before wrapping. Use `false` to never wrap, or `true` to always wrap.
  opts [String]  indent      ("  ")  Whitespace used to indent each level when wrapping (without the :short option).
  opts [Boolean] indent_last (false) Indent the closing bracket for arrays and objects (without the :short option).
  opts [Boolean] short       (false) Keep the output 'short' when wrapping, putting opening brackets on the same line as the first value, and closing brackets on the same line as the last item.
  opts [Boolean] sort        (false) Sort the keys for objects to be in alphabetical order (`true`), or supply a lambda to determine ordering.
  opts [Boolean] aligned     (false) When wrapping objects, align the colons (only per object).
  opts [Integer] decimals     (null) Decimal precision to use for floats; omit to keep numberic values precise.
  opts [Integer] padding         (0) Number of spaces to put inside brackets/braces for both arrays and objects.
  opts [Integer] array_padding   (0) Number of spaces to put inside brackets for arrays. Overrides `:padding`.
  opts [Integer] object_padding  (0) Number of spaces to put inside braces for objects. Overrides `:padding`.
  opts [Integer] around_comma    (0) Number of spaces to put before/after commas (for both arrays and objects).
  opts [Integer] before_comma    (0) Number of spaces to put before commas (for both arrays and objects).
  opts [Integer] after_comma     (0) Number of spaces to put after commas (for both arrays and objects).
  opts [Integer] around_colon    (0) Number of spaces to put before/after colons (for objects).
  opts [Integer] before_colon    (0) Number of spaces to put before colons (for objects).
  opts [Integer] after_colon     (0) Number of spaces to put after colons (for objects).
  opts [Integer] around_colon_1  (0) Number of spaces to put before/after colons for single-line objects.
  opts [Integer] before_colon_1  (0) Number of spaces to put before colons for single-line objects.
  opts [Integer] after_colon_1   (0) Number of spaces to put after colons for single-line objects.
  opts [Integer] around_colon_n  (0) Number of spaces to put before/after colons for multi-line objects.
  opts [Integer] before_colon_n  (0) Number of spaces to put before colons for multi-line objects.
  opts [Integer] after_colon_n   (0) Number of spaces to put after colons for multi-line objects.
  opts [String] the JSON representation of the object.

  The lambda for the `sort` option will be passed the string name of the key, the value, and the hash for the object being sorted.
  The values returned for all keys must be all comparable, or an error will occur.
  """
  def rb(val):
    return not((val is None) or (val is False))
  def chain(*c):
    if not c:
      raise Exception('Empty chain')
    r = None
    for t in c:
      z = None
      if isinstance(t,tuple):
        o,k = t
        if k in o:
          z = o[k]
        else:
          continue
      else:
        z = t
      if rb(z):
        r = z
        break
    return r
  def setchain(o,k,*c):
    o[k] = chain((o,k),*c)
    return o[k]

  if 'wrap' not in opts:
    opts['wrap'] = 80
  elif opts['wrap'] is True:
    opts['wrap'] = -1
  setchain(opts,'indent','  ')
  setchain(opts,'array_padding',(opts,'padding'),0)
  setchain(opts,'object_padding',(opts,'padding'),0)
  setchain(opts,'after_comma',(opts,'around_comma'),0)
  setchain(opts,'before_comma',(opts,'around_comma'),0)
  setchain(opts,'before_colon',(opts,'around_colon'),0)
  setchain(opts,'after_colon',(opts,'around_colon'),0)
  setchain(opts,'before_colon_1',(opts,'around_colon_1'),(opts,'before_colon'),0)
  setchain(opts,'after_colon_1',(opts,'around_colon_1'),(opts,'after_colon'),0)
  setchain(opts,'before_colon_n',(opts,'around_colon_n'),(opts,'before_colon'),0)
  setchain(opts,'after_colon_n',(opts,'around_colon_n'),(opts,'after_colon'),0)

  if re.match(r"\S",opts['indent']):
    raise Exception("indent option must only whitespace")

  apad   = " " * opts['array_padding']
  opad   = " " * opts['object_padding']
  comma  = "{},{}".format(' '*opts['before_comma'],' '*opts['after_comma'])
  colon1 = "{}:{}".format(' '*opts['before_colon_1'],' '*opts['after_colon_1'])
  colonn = "{}:{}".format(' '*opts['before_colon_n'],' '*opts['after_colon_n'])

  objid  = {}
  memo   = {}
  def memoize(o):
    i = None
    if o not in objid.values():
      objid[len(objid.items())] = o
    i = objid.values().index(o)
    return i
  def build(o,indent):
    mi = memoize((o,indent))
    if mi not in memo:
      if isinstance(o,str) or isinstance(o,int):
        memo[mi] = "{}{}".format(indent,json.dumps(o))
      elif isinstance(o,bool):
        memo[mi] = "{}{}".format(indent,repr(o).lower())
      elif o is None:
        memo[mi] = "{}{}".format(indent,'null')
      elif isinstance(o,float):
        if o.is_integer() and "e" not in str(o):
          memo[mi] = build(int(o),indent)
        elif 'decimals' in opts and isinstance(opts['decimals'],int):
          memo[mi] = "{}{:.{}f}".format(indent,opts['decimals'],o)
        else:
          memo[mi] = "{}{}".format(indent,repr(o))
      elif isinstance(o,list):
        if not o:
          memo[mi] = "{}{}".format(indent,'[]')
        else:
          pieces = [build(v,'') for v in o]
          ol = "{}[{}{}{}]".format(indent,apad,comma.join(pieces),apad)
          if not opts['wrap'] or len(ol) <= opts['wrap']:
            memo[mi] = ol
          elif opts.get('short'):
            indent2 = "{} {}".format(indent,apad)
            pieces = [build(v,indent2) for v in o]
            pieces[ 0] = pieces[ 0].replace(indent2,"{}[{}".format(indent,apad),1)
            pieces[-1] = "{}{}]".format(indent,apad)
            memo[mi] = ",\n".join(pieces)
          else:
            indent2 = "{}{}".format(indent,opts['indent'])
            memo[mi] = "{}[\n{}\n{}]".format(
              indent,
              ",\n".join(build(v,indent2) for v in o),
              indent2 if rb(opts.get('indent_last')) else indent
            )
          pass
      elif isinstance(o,dict):
        if not o:
          memo[mi] = "{}{}".format(indent,o)
        else:
          sort = chain((opts,'sorted'),(opts,'sort'))
          if sort is True:
            #key sort
            s = sorted(o.items())
          elif callable(sort):
            arity = len(inspect.getargsspec(sort).args)
            if arity > 1:
              s = sorted(o.items(),key=lambda v:sort(*v))
            elif arity == 1:
              s = sorted(o.items(),key=lambda k:sort(*k))
            pass
          else:
            s = list(o.items())
          # 
          kv = [(build(str(k),''),build(v,'')) for k,v in s]
          ol  = "%s{%s%s%s}" % (indent,opad,comma.join(colon1.join(kvp) for kvp in kv),opad)
          # 
          idp = ['']
          def sconv(k,v):
            ol  = "{}{}{}".format(k,colonn,build(v,''))
            if opts.get('wrap') and (len(ol) > opts.get('wrap')) and (isinstance(v,list) or isinstance(v,dict)):
              return "{}{}{}".format(k,colonn,build(v,idp[0]).lstrip())
            else:
              return ol
          def aconv(kvp):
            longest = max(len(k) for k,v in kvp)
            formatk = "%%-%ds" % longest
            
            del kv[:]
            kv.extend((formatk % k,v) for k,v in kvp)
            return kv
          #
          if not opts['wrap'] or len(ol) <= opts['wrap']:
            memo[mi] = ol
          elif opts.get('short'):
            del kv[:]
            kv.extend(("{} {}{}".format(indent,opad,build(str(k),'')),v) for k,v in s)
            kv[0][0] = kv[0][0].replace("{}{}".format(indent,' '),"{}{}".format(indent,'{'),1)
            if opts.get('aligned'):
              aconv(kv[:])
            def iconv(k,v):
              idp[0] = " "*len("{}{}".format(k,colonn))
              return sconv(k,v)
            skv = [iconv(k,v) for k,v in kv]
            memo[mi] = "{}{}{}".format(indent,",\n".join(skv),'}')
          else:
            del kv[:]
            kv.extend(("{}{}{}".format(indent,opts['indent'],build(str(k),'')),v) for k,v in s)
            if opts.get('aligned'):
              aconv(kv[:])
            idp[0] = '{}{}'.format(indent,opts['indent'])
            skv = [sconv(k,v) for k,v in kv]
            memo[mi] = "{}{}\n{}\n{}{}".format(
              indent, '{',
              ",\n".join(skv),
              idp[0] if opts.get('indent_last') else indent,
              '}'
            )
          pass
        pass
      else:
        memo[mi] = build(o.__dict__,indent)
    return memo[mi]
  return build(obj, '')