Python & Data debugging
From circular imports and the GIL to Django ORM N+1s, FastAPI validation, asyncio, and pandas/PyTorch shape and memory traps.
36 guides·5 playable labs
Playable labs
The File That Left the VaultA document download endpoint serves more than the vault folder.Security · MediumThe Dashboard That Averaged AveragesOn-call swears p95 is fine. Customers still time out.Observability · MediumThe Config That Swallowed ProdProduction boots with the dev database URL and debug flags.Config & Environment · MediumThe Redirect That Left the BuildingLogin next= parameter sends users to attacker-controlled hosts.Security · MediumThe Webhook That Trusted SilenceUnsigned webhook deliveries are accepted when the signature header is missing.Security · Medium
Debugging guides
Diagnosing Silent Failures and Deadlocks in Python AsyncioPython · AdvancedPython Circular Import Error: Debugging the Dependency CyclePython · IntermediatePython GIL Debugging: When Threads Don't Really Run in ParallelPython · AdvancedDjango ORM N+1 Query Debugging: Finding and Fixing Hidden Database BloatPython · IntermediateDjango Static Files Not Serving in ProductionPython · BeginnerDjango Authentication Not Working: A Systematic Debugging GuidePython · IntermediateFastAPI Dependency Injection Fails: Missing `async def` and Scope MismatchesPython · IntermediateDjango Celery Task Not Executing: A Field Guide to Silent FailuresPython · IntermediateDebugging FastAPI 422 Validation Errors: Pydantic Model MismatchesPython · IntermediateFastAPI Background Task Not Running: Debugging Silent FailuresPython · IntermediatePython Multiprocessing PicklingError: How to DebugPython · AdvancedPython Decorator Losing Function Metadata: __name__, __doc__, and __wrapped__Python · IntermediatePython Context Manager Not Releasing Resource: Debugging GuidePython · IntermediateDebugging Mutable Default Arguments in Python DataclassesPython · IntermediatePython logging not showing output: Why your log messages vanishPython · IntermediateDebugging Pytest Fixture Scope MismatchesPython · IntermediatePython Mock patch() Wrong Target: Why Your Mock Isn't MockingPython · IntermediateNumPy Broadcasting Shape Mismatch: A Field Guide to Silent Failures and Runtime ErrorsPython · IntermediatePandas dtype Unexpected Conversion: A Debugging GuidePython · IntermediateDebugging Python Datetime Timezone-Awareness and Offset ErrorsPython · IntermediateCelery Beat Periodic Task Not Running: A Field GuidePython · IntermediatePython Virtual Environment Package Not Found: Debugging GuidePython · BeginnerPython UnicodeEncodeError / UnicodeDecodeError: A Field GuidePython · IntermediatePython Generator Already Exhausted: What You're Actually SeeingPython · IntermediatePydantic V2 Migration Breaking Changes Debugging GuidePython · IntermediateDebugging redis-py Connection Refused ErrorsPython · IntermediateDebugging LangChain Chain Output Errors: A Practical GuidePython · IntermediateDjango Migration Conflict Error: How to Diagnose and ResolvePython · IntermediatePyTorch CUDA Out of Memory: Diagnosis and RecoveryML / Data · AdvancedDebugging PyTorch Tensor Shape Mismatch Runtime ErrorsML / Data · IntermediatePyTorch Gradient Explosion Producing NaN LossML / Data · AdvancedTensorFlow Incompatible Shapes Error: Debugging Shape Mismatch in ProductionML / Data · IntermediateDiagnosing NumPy MemoryError When Allocating Large ArraysML / Data · IntermediateJupyter Kernel Keeps Dying: Debugging and Fixes GuideML / Data · IntermediateDebugging Pandas Merge Producing Duplicate RowsML / Data · IntermediatePandas SettingWithCopyWarning: How to Find and Fix the Real SourceML / Data · Intermediate