Python remove empty and null keys doesn't effect my object

Question

I'm trying to remove null and empty keys from my python object by calling a method from a module.

from file2 import remove_nulls
# initialize object and set attributes
obj.remove_nulls()

In my remove_nulls() method, if I print the resultant object, I can observe that null and empty keys are removed, but after returning from the function, the final object still has the null and empty keys.

def remove_null(feature):
    return json.dumps(del_none(feature.__dict__.copy()))

def del_none(d):
  for key, value in list(d.items()):
    if value is None:
        del d[key]
    elif isinstance(value, dict):
        del_none(value)
  return d

Can someone help to fine where it went wrong?

Your `return` is inside the `for` loop. It should be after it. — khelwood, Oct 11 '18 at 12:11
.. and neither of the functions you've included are the ones being called, since you call a method on the object `obj`, and neither the `remove_null(feature)` function or the `del_none(d)` function matches the signature (.. or is part of a class) — MatsLindh, Oct 11 '18 at 12:22
@MatsLindh, i've not put my exact code, it's just an example to explain the flow, the method is called in my code, if i print the object before return statement, i can see that the null values are removed, but after calling the method in my file, if i print the object i can see that the nulls still exists. — siri, Oct 11 '18 at 12:24

Jean-François Fabre · Answer 1 · 2018-10-11T12:43:09.480

Just too many copies...:

def remove_null(feature):
    return json.dumps(del_none(feature.__dict__.copy()))

that applies del_none on a copy of your object, dumps the proper "cleaned" object, then returns, leaving your object untouched (since you created a copy). You probably need to do just:

def remove_null(feature):
    return json.dumps(del_none(feature.__dict__))

The confusion probably comes from the need to copy the dictionary keys+values to avoid removing items on a dict while iterating on it (which was probably handled here, at the wrong level, then handled at the proper level, but the first copy was not removed)

Python remove empty and null keys doesn't effect my object

1 Answers1