Feature Request: no newlines in base lists

[jessexknight]

I have some content with long and sometimes deeply nested lists (from np.ndarray.tolist()). While it is readable to print with newlines for every element, it would IMO be much cleaner to omit newlines in the inner-most list, and replace with spaces. For example,

Currently:

{
 "arr": [
  [
   0.0,
   null,
   0.468
  ],
  [
   0.0,
   null,
   0.688
  ],
  [
   0.0,
   0.32,
   null
  ],
  [
   0.0,
   0.25,
   null
  ]
 ]
 }
}

Desired:

{
 "arr": [
  [ 0.0, null ,0.468 ],
  [ 0.0, null, 0.688 ],
  [ 0.0, 0.32, null ],
  [ 0.0, 0.25, null ]
 ]
}

Would this be considered? Or too much of a special case?
Thanks,

[etrepum]

It’s an interesting use case, but pretty printing is a bit complicated in the general case. If you had a PR to implement this it would be strongly considered so long as it doesn’t affect performance of the normal case.

[jessexknight]

I'll see what I can do when I get some free time!

FYI, for now, my workaround looks like this (I also only want to "flatten" numeric arrays):

import re,simplejson
# ...
def jsondump(obj,fp,**kwargs):
  s = simplejson.dumps(obj,**kwargs)
  for match in re.finditer('\[((?ms)\n|\s|\d|\.|\,|null)*\]',s):
    s = s.replace(match.group(0),
                  match.group(0).replace(' ','').replace('\n',' '))
  fp.write(s)