CODEWITHSUNDEEP
pythondictionary
eneski
eneski

Reputation: 1655

Getting keys for specific a value in dictionary

The reason why I am asking this question is because I am working with huge datas.

In my algorithm, I basically need something like this:

users_per_document = []
documents_per_user = []

As you understand it from the names of the dictionaries, I need users that clicked a specific document and documents that are clicked by a specific user.

In that case I have "duplicated" datas, and both of them together overflows the memory and my script gets killed after a while. Because I use very large data sets, I have to make it in a efficient way.

I think that is not possible but I need to ask it, is there a way to get all keys of a specific value from dictionary?

Because if there is a way to do that, I will not need one of the dictionaries anymore.

For example:

users_per_document["document1"] obviously returns the appropriate users,
what I need is users_per_document.getKeys("user1") because this will basically return the same thing with documents_per_user["user1"]

If it is not possible, any suggestion is pleased..

Upvotes: 0

Views: 60

Answers (2)

Jack Ryan
Jack Ryan

Reputation: 1318

If you are using Python 3.x, you can do the following. If 2.x, just use .iteritems() instead.

user1_values = [key for key,value in users_per_document.items() if value == "user1"]

Note: This does iterate over the whole dictionary. A dictionary isn't really an ideal data structure to get all keys for a specific value, as it will be O(n^2) if you have to perform this operation n times.

Upvotes: 1

user7089924
user7089924

Reputation:

I am not very sure about the python, but in general computer science you can solve the problem with the following way;

Basically, you can have three-dimensional array, first index is for users , second index for documents and the third index would be a boolean value.

The boolean value represents if there is relation between the specific user and the specific document.

PS: if you have really sparse matrix, you can make it much more efficient, but it is another story

Upvotes: 0

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