Memory Leak in Python: Unbounded growth due to closures or default mutable arguments

My Python application gradually consumes more memory over time, even though objects should be garbage collected. What causes this leak, and how can I diagnose or fix it?

True memory leaks in Python are rare, but retention of unwanted references makes it appear like leaks happen. Common culprits: • Closures binding unnecessary context, unintentionally retaining large objects or entire instances within callbacks. Persistent event handlers or DB callbacks can hold closures alive far longer than expected Reddit+2Index+2Stack Overflow+2GeeksforGeeksStack Overflow. • Mutable default arguments like def foo(a=[]): the same list is reused across calls, growing without bound Stack Overflow. 🛠️ How to Fix • Avoid mutable default args: python Copy code def foo(a=None): a = a or [] ... • Use weak references (weakref) or datatypes (e.g. WeakKeyDictionary) to break strong reference cycles, especially in observer patterns RedditWikipedia+1GeeksforGeeks+1. • Explicitly remove or nullify closures or callbacks when no longer needed. • Employ profiling tools like tracemalloc to locate allocation hotspots and lingering references Reddit+2Stack Overflow+2Stack Overflow+2Reddit+2Snyk+2arXiv+2.