在 python 字典中替换 None

Question

I happen to have a complex dictionary (having lists, dicts within lists etc). The values for some of the keys are set as None

Is there a way I can replace this None with some default value of my own irrespective of the complex structure of the dictionary?

Answer 1

You can do it using object_pairs_hook from json module:

def dict_clean(items):
    result = {}
    for key, value in items:
        if value is None:
            value = 'default'
        result[key] = value
    return result

dict_str = json.dumps(my_dict)
my_dict = json.loads(dict_str, object_pairs_hook=dict_clean)

Answer 2

# replace_none_with_empty_str_in_dict.py

raw = {'place': 'coffee shop', 'time': 'noon', 'day': None}

def replace_none_with_empty_str(some_dict):
    return { k: ('' if v is None else v) for k, v in some_dict.items() }

print(replace_none_with_empty_str(raw))

Answer 3

Recursive solution from Lutz:

def replace(any_dict):
    for k, v in any_dict.items():
        if v is None:
            any_dict[k] = "my default value"
        elif type(v) == type(any_dict):
            replace(v)

replace(my_dict)

Answer 4

for k, v in my_dict.items():
    if v is None:
        my_dict[k] = "my default value"

Answer 5

You could do it with recursive function that iterates over all dicts and lists:

def convert(obj):
    if type(obj) == list:
        for x in obj:
            convert(x)
    elif type(obj) == dict:
        for k, v in obj.iteritems():
            if v is None:
                obj[k] = 'DEFAULT'
            else:
                convert(v)

data = {1: 'foo', 2: None, 3: [{1: 'foo', 2: None}]}
convert(data)
print data # -> {1: 'foo', 2: 'DEFAULT', 3: [{1: 'foo', 2: 'DEFAULT'}]}

Answer 6

Here's a recursive solution that also replaces None s inside lists.

First we define a simple class, Null , to act as the replacement for None .

class Null(object):
    def __repr__(self):
        return 'Null'

NULL = Null()

def replace_none(data):
    for k, v in data.items() if isinstance(data, dict) else enumerate(data):
        if v is None:
            data[k] = NULL
        elif isinstance(v, (dict, list)):
            replace_none(v)

# Test
data = {
    1: 'one', 
    2: ['two', 2, None], 
    3: None, 
    4: {4: None, 44: 'four'},
    5:  {
            5: [55, 56, None], 
            6: {66: None, 67: None},
            8: [88, {9:'nine', 99:None}, 100]
        }
}

print(data)
replace_none(data)
print(data)

output

{1: 'one', 2: ['two', 2, None], 3: None, 4: {44: 'four', 4: None}, 5: {8: [88, {9: 'nine', 99: None}, 100], 5: [55, 56, None], 6: {66: None, 67: None}}}
{1: 'one', 2: ['two', 2, Null], 3: Null, 4: {44: 'four', 4: Null}, 5: {8: [88, {9: 'nine', 99: Null}, 100], 5: [55, 56, Null], 6: {66: Null, 67: Null}}}