if not x: is slightly faster and checks if x is "falsy" (e.g., False, None, 0, "", [], etc.).
if x == False: explicitly checks if x is False, but is marginally slower due to the additional comparison operation.
When to Use Each:
Use if not x: for checking if x is falsy.
Use if x is False: (instead of == for identity checks) only to explicitly check for False.