Locks

A lock is the simplest tool for keeping threads from stepping on each other. When two threads try to update the same variable, the result depends on the exact interleaving of their instructions, and updates can disappear without any error being raised. threading.Lock makes a block of code run as one indivisible unit. This lesson covers Lock itself: when one is needed, how to use it correctly, how RLock differs, what the GIL does and doesn't protect, and what lock contention costs.