Get list value by comparing values

Question

I have a list like this:

    data.append(
        {
            "type": type,
            "description": description,
            "amount": 1,
        }
    )

Every time there is a new object I want to check if there already is an entry in the list with the same description. If there is, I need to add 1 to the amount.

How can I do this the most efficient? Is the only way going through all the entries?

you could make data as a dictionary and have the description be the key. — ewokx, Jul 07 '20 at 07:05
I would say making description value as key would be a bad idea since descriptions can be of any length — bigbounty, Jul 07 '20 at 07:09
@bigbounty I have it as a value now? What exactly do you mean? thanks for the help! — sg_sg94, Jul 07 '20 at 07:10
@ewong as bigbounty mentioned, that's not ideal. The description can be 250 char long. — sg_sg94, Jul 07 '20 at 07:19
In that case, you could always make data as a dictionary and the hash of the description as the key. — ewokx, Jul 07 '20 at 07:33
@ewong I don't think that explicitly hashing the string improves performance right? This is what `dict` does under the hood. — orestisf, Jul 07 '20 at 09:28

score 1 · Answer 1 · answered Jul 07 '20 at 08:11

I suggest making data a dict and using the description as a key.

If you are concerned about the efficiency of using the string as a key, read this: efficiency of long (str) keys in python dictionary.

Example:

data = {}
while loop():  # your code here
    existing = data.get(description)
    if existing is None:
        data[description] = {
            "type": type,
            "description": description,
            "amount": 1,
        }
    else:
        existing["amount"] += 1

In either case you should first benchmark the two solutions (the other one being the iterative approach) before reaching any conclusions about efficiency.

Get list value by comparing values

1 Answers1