Under what circumstances does the automatic memory management mechanism free objects that are no longer referenced?

In Python, the automatic memory management mechanism (garbage collector) frees objects that no longer have active references, meaning when the reference count of an object becomes zero.

This occurs in the following cases:

• All variables and data structures referencing the object cease to exist or are reassigned.
• The object is not accessible from the current program context.

Example:

obj = [1, 2, 3]
ref = obj  # reference count increases

del obj     # reference count decreases
ref = None  # reference count becomes 0, object is freed

Besides reference counting, Python uses an additional cyclic reference collector to free objects that reference each other but are not accessible from the program.

Thus, an object is freed when there are no active references to it, and the garbage collector automatically clears the memory.