CODEWITHSUNDEEP
pythondictionary
Harrison
Harrison

Reputation: 2670

Add a key to the dict if not exist, then rename this key

Say I have a list of dicts:

ls = [{'id': 1, 'a1': 2, 'a2': 3}, {'id':2, 'a2':4}, {'id':3, 'a2':5}]

where a1 doesn't exist in some dicts

I want to set a1 to 0 in these dicts where a1 is missing and change the key name a1 to b1 in all dicts. Here is the code I come up with

for l in ls:
    l.setdefault('a1', 0)
    l['b1'] = l.pop('a1')

I'm wondering is it possible to make it more efficient, as I need to run this piece of code millions of times. Any improvements would be appreciated.

Upvotes: 1

Views: 285

Answers (1)

mhawke
mhawke

Reputation: 87074

Here is a slight improvement which exploits the fact that dict.pop() can take an argument to return as the default if the key is not in the dictionary:

ls = [{'id': 1, 'a1': 2, 'a2': 3}, {'id':2, 'a2':4}, {'id':3, 'a2':5}]
for d in ls:
    d['b1'] = d.pop('a1', 0)

>>> ls
[{'a2': 3, 'id': 1, 'b1': 2}, {'a2': 4, 'id': 2, 'b1': 0}, {'a2': 5, 'id': 3, 'b1': 0}]

Upvotes: 6

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