Setting default value in Python dictionary if key is missing

Question

Given a dictionary I need to check if certain keys exists, if they do I need to get their value, if they don't, then I have to set a default value. I am currently using this code:

if 'key1' in my_dict:
    pass
else:
    my_dict['key1'] = 'Not Available'

if 'key2' in my_dict:
    pass
else:
    my_dict['key2'] = 'Not Available'

if 'key3' in my_dict:
    pass
else:
    my_dict['key3'] = 'Not Available'

if 'key4' in my_dict:
    pass
else:
    my_dict['key4'] = 'Not Available'

This is of course painful, I guess I could iterate over the entire dictionary keys and check if the keys of interest are present, and if not, then set them. So the question is, is there a better way to do this? By this I mean, go through a large dictionary, check for keys, if they are not present set them to 'Not Available'.

Well, for starters, here you should use if key not in my_dict: my_dict[key] = "not available instead of checking the opposite and passing — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Apr 28, 2022 at 21:58
But there are various ways to handle default values in dict objects, the easiest being using my_dict.get(key, default_value) when you want to retreive the value of a key that may not be there — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Apr 28, 2022 at 21:59
Does this answer your question? setting the missing values of dictionary with default value python — mkrieger1
– mkrieger1, Commented Jul 31, 2023 at 16:40

blueshift · Accepted Answer · 2023-04-05 00:58:53Z

6

You can use the setdefault method

my_dict = {"a":1,"b":2}

If a key exists, there is no change made to the existing value

my_dict.setdefault('a', 3)
print(my_dict) #{'a': 1, 'b': 2}

If it doesn't exist, the key-value pair is added

my_dict.setdefault('c', 3)
print(my_dict) #{'a': 1, 'b': 2, 'c': 3}

Looping through multiple keys :

my_dict = {"a":1,"b":2}
keys = ["a","c","d"]
for key in keys:
    my_dict.setdefault(key, "Not Available")

print(my_dict) #{'a': 1, 'b': 2, 'c': 'Not Available', 'd': 'Not Available'}

edited Apr 5, 2023 at 0:58

blueshift

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answered Apr 28, 2022 at 22:00

Sruthi

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Comments

Sash Sinha · Accepted Answer · 2022-04-28 21:56:15Z

4

You could use dict.get(key[, default]):

>>> d = {'key1': 'apple'}
>>> d['key1']
'apple'
>>> d.get('key2', 'Not Available')
'Not Available'

answered Apr 28, 2022 at 21:56

Sash Sinha

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