RecursionError: maximum recursion depth exceeded

Python's recursion limit defaults to 1000 call frames — notably low compared to Node.js (approximately 10,000) and most compiled languages. This limit trips developers processing hierarchical data structures: JSON trees with nesting depth greater than 1000, file system traversal of deeply nested directories, recursive XML parsers, or graph algorithms on dense networks. The limit is intentional. Python does not perform tail-call optimization, so each recursive call adds a non-recoverable stack frame. Python raises RecursionError before reaching the OS stack limit to give you a catchable exception rather than a segmentation fault. sys.setrecursionlimit(5000) raises the limit, but this should be paired with threading.stack_size(67108864) (64 MB) to avoid an actual OS-level stack overflow at high limits. A cleaner long-term fix is converting recursive algorithms to iterative ones using an explicit stack — a Python list or collections.deque used as a LIFO stack: push child nodes, pop and process, repeat. This pattern processes arbitrarily deep trees without hitting any recursion limit and typically runs faster due to reduced function call overhead. functools.lru_cache on memoized recursive functions can reduce effective call depth when the same subproblems recur (dynamic programming patterns), but it does not help for tree traversal where all nodes are unique. For graph algorithms, explicitly tracking visited nodes with a set prevents infinite recursion from cycles.