Israeli Queue

A Python implementation of the Israeli Queue, a priority queue variant where elements join behind the last member of their group rather than at the back of the line.

How it works

In a standard queue, new elements always go to the back. In an Israeli Queue, an element's position depends on whether its group is already represented in the queue. If it is, the element joins immediately after the last member of its group. If not, it goes to the back.

This models real-world queuing behavior where people join their friends already in line rather than starting a new position at the back.

Installation

pip install IsraeliQueue

Usage

Basic queue

from IsraeliQueue import Item, IsraeliQueue

queue = IsraeliQueue()

alice = Item("Alice", group=1)
charlie = Item("Charlie", group=2)
bob = Item("Bob", group=1)

queue.enqueue(alice)    # [Alice]
queue.enqueue(charlie)  # [Alice, Charlie]
queue.enqueue(bob)      # [Alice, Bob, Charlie] — Bob joins his group, not the back

print(queue)  # [Alice, Bob, Charlie]

Explicit placement

Use put() to place an item directly after a specific friend:

queue.put(bob, alice)  # Bob joins immediately after Alice

Type-based grouping

IsraeliQueueByType automatically groups elements by their Python type:

from IsraeliQueue import IsraeliQueueByType

queue = IsraeliQueueByType()

queue.enqueue("hello")
queue.enqueue(42)
queue.enqueue("world")
queue.enqueue(99)

print(queue)  # [["hello", "world"], [42, 99]]

API

Testing

pytest --cov=IsraeliQueue --cov-report=term-missing

97% coverage across 38 tests covering edge cases, error conditions, and performance.

Contributing

Issues and pull requests are welcome. For significant changes, open an issue first.

License

MIT — see LICENSE.txt