CODEWITHSUNDEEP
pythondictionarydefault
Neel
Neel

Reputation: 21243

Get default value if key has falsy value in dict

I am working in python, and was using dict in my code.

I have case where I always need default value if the give key is not exist or if key exists and it has falsy value.

for example

x = {'a': 'test', 'b': False, 'c': None, 'd': ''}
print x.get('a', [])
test
print x.get('b', []) # Need [] as False is falsy value in python
False 
print x.get('e', []) # This will work fine, because `e` is not valid key
None
print x.get('c', []) 
None
print x.get('c', []) or [] # This gives output which I want

Instead of check Falsy value in or operation, is there any pythonic way to get my default value?

Upvotes: 2

Views: 1412

Answers (2)

Frodon
Frodon

Reputation: 3775

Here is an ugly hack:

from collections import defaultdict

x = {'a': 'test', 'b': False, 'c': None, 'd': ''}
d = defaultdict(lambda : [], dict((k, v) if v is not None else (k, []) for k, v in x.items()))
print(d['a'])
# test
print(d['b'])
# False
print(d['e'])
# []
print(d['c']) 
# []

Upvotes: 0

Moses Koledoye
Moses Koledoye

Reputation: 78546

Using or to return your default value is Pythonic. I'm not sure you will get a more readable workaround.

About using or in the docs:

This is a short-circuit operator, so it only evaluates the second argument if the first one is False.

You must also consider that the value must have been accessed first before it can then be evaluated as Falsy or Truthy.

Upvotes: 4

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