replacing deleting empty values from dict, list recursively in python

Question

I have written the below code for the task of removing every Null or empty content. The script works, however I think it is not "pytonish" at all. How would be the python way to do it ?

def remove_empty_values(ret):
    #ret is assumed eitehr dict or list
    #recursively remove all key or list items which values is Null or empty string
    if type(ret) == list:
            empty_indexes=[]
            i = 0
            for index in ret:
                    if (ret[i] == None) or ((type(ret[i]) == str and  ret[i] == '') or ((type(ret[i]) == unicode and  ret[i] == '') or (( type(ret[i])==dict or type(ret[i])==list )  and len(ret[i]) ==0))):
                            empty_indexes.append(i)
                    else:
                             if (type(ret[i])==dict or type(ret[i])==list):
                                    remove_empty_values(ret[i])
                    i = i + 1
            for index in empty_indexes:
                    del ret[index]

    elif type(ret) == dict:

            empty_keys=[]
            for key in ret:
                    if (ret[key] == None) or ((type(ret[key]) == str and ret[key] == '') or ((type(ret[key]) == unicode and ret[key] == '') or (( type(ret[key])==dict or type(ret[key])==list )  and len(ret[key]) ==0))):
                            empty_keys.append(key)
                    else:
                             if (type(ret[key])==dict or  type(ret[key])==list):
                                    remove_empty_values(ret[key])
            for key in empty_keys:
                    del ret[key]

@ScottHunter well it is too long for the task it does, the for cycle, the I = I +1, I was developing in C++ and I feel this is a C-Style code :) — Endre Magyari
– Endre Magyari, Commented Jun 29, 2020 at 13:59

Andrej Kesely · Accepted Answer · 2020-06-29 14:42:11Z

2

If you use Python 3.8+, you can use assignment expression :=:

For example:

d = {'a': [{'b': 'x', 'c': ''}], 'c': ['', '1', None], 'd': ['']}


def remove(i):
    if isinstance(i, dict):
        return {k: vv for k, v in i.items() if (vv:=remove(v))}
    elif isinstance(i, list):
        return [vv for v in i if (vv:=remove(v))]
    return i

print(remove(d))

Prints:

{'a': [{'b': 'x'}], 'c': ['1']}

EDIT: To keep zeros and False:

d = {'a': [{'b': 'x', 'c': ''}], 'c': ['', '1', None], 'd': ['', 0, False]}


def remove(i):
    if isinstance(i, dict):
        return {k: vv for k, v in i.items() if (vv:=remove(v)) or v is False or v == 0}
    elif isinstance(i, list):
        return [vv for v in i if (vv:=remove(v)) or v is False or v == 0]
    return i

print(remove(d))

Prints:

{'a': [{'b': 'x'}], 'c': ['1'], 'd': [0, False]}

edited Jun 29, 2020 at 14:42

answered Jun 27, 2020 at 21:46

Andrej Kesely

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2 Comments

Endre Magyari Over a year ago

But this would kill the boolean false values is, wouldn't it ?

Endre Magyari Over a year ago

I need to keep the 0s and the explicit boolean false values as well

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