implementation of __getitem__ in PriorityQueue

[goswami-rahul]

It essentially returns the same key if it is present, else returns None (doesn't raise Exception).
Is this the intended use?

def __getitem__(self, key):
        for _, item in self.A:
            if item == key:
                return item

Also, the documentation of PriorityQueue says
It supports dict-like lookup.

What exactly is the method __getitem__ trying to do (and return)?

[thesagarsehgal]

@goswami-rahul I was just seeing the function, and I wasn't able to figure out what will be the use of the __getitem__ function. Like we are giving value and getting that itself as output if it is there in the PriorityQueue. It means the same thing as __contains__ does i.e. to find if an element is there in the Queue or not. Instead of doing like this returning the value at an index would be better.

[rajatjain1997]

@sagar-sehgal The getitem function works quite differently than contains. We might just need both of them for different algorithms here.

Example:
Take two objects (a and b) of the same class, they will be stored as: ( f_val:1, id:1), (f_val:2, id:1). Here the same id implies that the objects are equal according to their eq function, but have a different f-value in the queue. Further, let us assume that a is in the queue and the second one isn't.

contains(b): Returns false! Because the f-value does not match that of a
get_item(b): Returns a! Because they are equal according to their class definition and only their f-value differs.

[dmeoli]

PriorityQueue.getitem is implemented in utils.py. Closing as resolved.