All 15 Memory Management & Garbage Collection questions
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How does the gc module let you inspect and debug memory leaks caused by uncollectable objects?

Intermediate

Answer

gc.collect() returns the number of unreachable objects it found and collected; gc.garbage lists objects the collector found uncollectable (in older Python versions, mainly ones with __del__ methods in cycles). gc.set_debug(gc.DEBUG_LEAK) and get_objects()/get_referrers() help trace what's holding references to unexpectedly long-lived objects during memory leak investigation.
import gc

gc.set_debug(gc.DEBUG_STATS)
unreachable = gc.collect()
print(f'Collected {unreachable} unreachable objects')
print(gc.garbage)  # objects that couldn't be collected
Real-world example A long-running service investigates a slow memory leak by periodically calling gc.collect() and logging gc.garbage to identify which custom classes with __del__ methods are stuck in uncollectable cycles.

Common follow-ups: How do you use gc.get_referrers() to trace what's keeping an object alive?;What tools like objgraph help visualize reference graphs?

Debugging & Profiling;Multiple Inheritance & MRO
All 15 Memory Management & Garbage Collection questions