CODEWITHSUNDEEP
python
visc
visc

Reputation: 4959

Get value from call to any

I have a list of objects and they all have a data member visited.

visited is a boolean, default is False.

I would like to be able to iterate over the list of objects to find an object that has not been visited.

If all the objects have been visited I want to detect that and set another boolean called done_searching to False.

Here is some pseudo code of what I'm trying to accomplish.

done_searching = False
while not done_searching:
    objects = [object1, object2, object3]

    foreach object in objects:
        if object.visited == False:
            non_visited_object = object
            break
        else if object.visited == True and last object in list
            done_searching = True
            break out of foreach

    non_visited_object.do_something()

    if (done_searching == True)
        break out of main

I also had an idea that I could somehow use any()... But it doesn't appear to work that way. Understandable loss of scope is the issue..

For example:

if any(object.visited == False for object in objects):
    object.do_something()
else
    searching_done = True

Upvotes: 0

Views: 48

Answers (2)

Linuxios
Linuxios

Reputation: 35803

To get the first element of an array matching a criterion, use this: 

next(obj for obj in objects if not obj.visited)

To have it return None if nothing is found, as @DSM said, use the default parameter:

next((obj for obj in objects if not obj.visited), None)

If the default parameter is omitted, next will raise a StopIteration exception if no objects are found matching the criteria.

Upvotes: 3

alexgolec
alexgolec

Reputation: 28252

any returns true if any of the entries in the array are true. The object variable is scoped inside the any call, so it's not visible outside of it. You can use a generator to accomplish this:

not_visited = (obj for obj in objects if not obj.visited).next()
if not_visited is None:
    searching_done = True

This has the benefit of being concise and only performing exactly as many comparisons as necessary. It will also evaluate to None if no object satisfies the condition.

Upvotes: 0

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