How does Python manage memory and garbage collection?
Quick answer
CPython frees objects mainly through reference counting, deleting an object as soon as nothing refers to it, and uses a cyclic garbage collector to clean up groups of objects that reference each other.
Every object keeps a count of references to it. When the count reaches zero its memory is released immediately. This makes cleanup predictable, but reference counting cannot free cycles, such as two objects that point at each other. The gc module's generational collector periodically finds and frees those.
Memory leaks in Python are usually objects kept alive by long-lived references: global lists or dictionaries, caches without limits, or closures. Use weakref for caches that should not keep objects alive, __slots__ to shrink many small objects, generators to stream data, and tools such as tracemalloc to see what is allocating memory.