system.interfaces.queues module

Abstract queue interfaces (read, write, read-write) and the queue factory.

class system.interfaces.queues.ReadQueue

Bases: ABC, Iterator, Generic

ReadQueue is an API for queues you can read data from. This is an Iterator that can directly be used in for-loops.

abstractmethod pop() → ObjectType

Removes and returns the first element of the queue

abstractmethod close() → None

Closes the queue

abstractmethod set_memory_limit(memory_limit: int) → None

Sets the memory limit for the queue. This is useful for queues that are disk-based and can use a buffer in memory to speed up access. If the memory limit is set to 0, the queue should not use any memory buffer.

Parameters:

memory_limit – The memory limit in bytes to use for the queue.

class system.interfaces.queues.WriteQueue

Bases: ABC, Generic

WriteQueue is an API for queues you can write data to.

abstractmethod insert(entry: ObjectType) → None

Inserts an entry into the queue. Corresponds to the add() and put() methods of a container, also next(entry) in a push-based iterator.

abstractmethod flush() → int

Flushes the contents of the queue, e.g. to a file, i.e. writes the contents of the buffer to the file.

Returns:

The number of objects written to the file for this call to flush()

abstractmethod close() → None

Closes the queue and potentially any file(s) backing the queue.

abstractmethod size() → int

Returns the number of elements inserted into this queue so far.

Returns:

The number of elements inserted into this queue so far.

abstractmethod set_memory_limit(memory_limit: int) → None

Sets the memory limit for the queue. This is useful for queues that are disk-based and can use a buffer in memory to speed up access. If the memory limit is set to 0, the queue should not use any memory buffer.

Parameters:

memory_limit – The memory limit in bytes to use for the queue.

class system.interfaces.queues.ReadWriteQueue(memory_limit: int = 10000)

Bases: ReadQueue, WriteQueue, ABC, Generic

ReadWriteQueue is an API for queues that can be read from and can be written to.

reset() → None

Resets the queue to the initial state.

set_memory_limit(memory_limit: int) → None

See WriteQueue.set_memory_limit().

class system.interfaces.queues.QueueFactory

Bases: ABC, Generic

QueueFactory is an abstract factory class to create readwrite queues. You can use this class to create instances of the different queues and in particular to create queues that are either disk or memory based. This allows you to configure queue-based algorithms with different types of code, e.g. run merge sort either in memory or disk or on a key-value store or ….

abstractmethod get_queue_instance() → ReadWriteQueue

Returns a ReadWriteQueue instance.

Returns:

An instance of a subclass of ReadWriteQueue.