Thread safety is often overlooked when we start with Python for developing simple scripts. But the hidden monster will be unleashed when we try to run non-thread safe code in a multithreaded setup. We will discuss the problems which can happen when seemingly good code is run in a multithreaded environment. We will walk over the concept of race coditions, how Python’s GIL currently affects multithreading and will cover steps to fix thread unsafe code using synchronization primitives.