Python language
Mutable default argument
Writing def f(items=[]). The list is created once at definition time and shared across every call.
Why interviewers ask about it
A classic screening question. Use None as the default and build inside the body. Dataclasses raise at class-creation time instead, which is why they force field(default_factory=list).
Related terms
This term is part of the free Python Full-Stack interview preparation module - browse the full glossary for every definition.