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Garbage Collection in Python . - Posted By skuchekar (skuchekar) on 16th Apr 25 at 9:12am
Python Garbage Collection
Python garbage collection is the automatic deallocation of memory no longer used. Python employs reference counting and cycle detector to deallocate memory and remove unused objects. The following is a step-by-step explanation of how it works:

1. Reference Counting
Python maintains the count of references to each object in memory. Each object in Python maintains an associated reference count. Once an object's reference count falls to zero (i.e., there are no references to it left), it gets automatically destroyed, and its memory is released.

2. Cycle Detection
While reference counting is good for the majority of situations, it breaks down in the case when objects point back to each other, creating a cycle (circular references). For instance, if two objects point to each other, their reference count will never become zero, and they will never automatically be deleted.

Python employs a cycle detector in order to determine and break the circular references. It periodically traverses to check for objects in cycles and frees them.

3. Garbage Collector (GC) Module
Python also supplies the gc module for interaction with the garbage collector process. Using this module gives manual control of the garbage collector process, such as compelling it to execute a collection, prevent it, or examine collected objects.

Key Functions in the gc Module:
gc.collect(): Initiates a forced garbage collection cycle.
gc.get_count(): Supplies the total objects in each of the three generations.
gc.get_objects(): Provides a list containing all the objects being traced by the garbage collector.

gc.set_debug(): Enables you to turn debugging output for garbage collection on or off.

4. Generational Garbage Collection
Python's garbage collector implements a generational algorithm, wherein objects are partitioned into generations according to how long ago they were created. There are three generations:

Generation 0: Newly allocated objects.

Generation 1: Objects that survived the initial garbage collection.

Generation 2: Objects that have survived multiple garbage collections.

Younger objects (generation 0) are garbage collected more often than older ones (generation 2), according to the principle that longer-lived objects are less likely to be garbage.

5. Garbage Collection Tuning
You can control the garbage collector's behavior by changing its parameters:
gc.set_threshold() lets you control how often garbage collection happens in terms of the number of allocations and deallocations.

You can also force garbage collection with gc.collect().

Python garbage collection is a robust mechanism that employs reference counting and cycle detection for memory management. The gc module has functions to control and observe the garbage collection activity, and you can optimize or fine-tune its operation if necessary.



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