CODEWITHSUNDEEP
python
Olivier Pons
Olivier Pons

Reputation: 15778

One liner if an index doesnt exists

For a lot of objects before calling .append() I do something like:

if not d.get('turns'):
    d['turns'] = []

Is there a oneliner in Python to do this?

After some answers, here's my kind of code:

d = json.loads(str(self.data))
if not d.get('turns'):
    d['turns'] = []
d['turns'].append({
    'date': time_turn,
    'data': data
})

Upvotes: 1

Views: 55

Answers (4)

niemmi
niemmi

Reputation: 17263

You can use defaultdict:

from collections import defaultdict

d = defaultdict(list)
d['turns'] # []

Other option is to use setdefault:

d.setdefault('turns', []) # []
d.setdefault('turns', 'foo') # []

UPDATE Given the full code you could either write

d = defaultdict(list, json.loads(str(self.data)))
d['turns'].append({'date': time_turn, 'data': data})

or

d = json.loads(str(self.data))
d.setdefault('turns', []).append({'date': time_turn, 'data': data})

Upvotes: 4

timgeb
timgeb

Reputation: 78690

Is there a oneliner in Python to do this?

Yes

d.setdefault('turns', [])

Demo:

>>> d = {}
>>> d.setdefault('turns', [])
[] # the inserted value is also returned
>>> d
{'turns': []}

If the key is found, setdefault behaves like get:

>>> d['turns'].append(1)
>>> d.setdefault('turns', 'irrelevant')
[1]

Upvotes: 3

nathan.medz
nathan.medz

Reputation: 1603

depending on if the get is standard, it likely has the option to specify a default return if the item is not found, so

d.get('turns', [])

will give you the value if it exists, or [] if it doesn't.

Upvotes: 3

Aurel
Aurel

Reputation: 631

Well, you can "oneline" it using :

d['turns'] = [] if not d.get('turns')

Upvotes: 0

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