Python filter function - single result

python python-3.x built-in
Giannis picture Giannis · Apr 10, 2015 · Viewed 10.1k times · Source

Is there a built in function in Python that will return a single result given a list and a validation function?

For example I know I can do the following:

    resource = list(filter(lambda x: x.uri == uri, subject.resources))[0]

The above will extract a resource from a list of resources, based on ther resource.uri field. Although this field value is uinique, so I know that I will either have 1 or 0 results. filter function will iterate the whole list. In my case its 20 elements, but I want to know if there is some other built-in way to stop the iteration on first match.

Answer

ferhat elmas picture ferhat elmas · Apr 10, 2015

See https://docs.python.org/3/library/functions.html#next

next(iterator[, default])

Retrieve the next item from the iterator by calling its next() method. If default is given, it is returned if the iterator is exhausted, otherwise StopIteration is raised.

e.g. in your case:

resource = next(filter(lambda x: x.uri == uri, subject.resources), None)

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