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What does it mean that functions are 'first-class objects' in Python? What is Python's LEGB rule for variable scope resolution, and what does each letter stand for? Why do you need the 'global' keyword to MODIFY a global variable from inside a function, but not to simply READ it? How does the 'nonlocal' keyword let a nested function modify a variable in its ENCLOSING (not global) scope? Why is using a mutable default argument (like an empty list) a classic Python bug, and how do you avoid it? How do keyword-only arguments (using a bare '*' in the parameter list) force certain parameters to be passed by name only? How do positional-only parameters (using a bare '/' in the parameter list, Python 3.8+) restrict how certain parameters can be passed? How does a closure capture variables from its enclosing scope, and what pitfall occurs when creating multiple closures inside a loop? How do you use functools.partial to create a new function with some arguments pre-filled? How does Python evaluate default argument expressions ONLY ONCE at definition time, and what SAFE pattern exploits this for genuinely useful caching?
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How do *args and **kwargs let a function accept an arbitrary number of positional and keyword arguments?

Intermediate

Answer

*args collects any extra POSITIONAL arguments into a tuple; **kwargs collects any extra KEYWORD arguments into a dict — letting a function accept a flexible, variable number of arguments beyond its explicitly named parameters, commonly used for wrapper functions or highly generic APIs.
def flexible_function(required, *args, **kwargs):
    print(f"required={required}")
    print(f"args={args}")
    print(f"kwargs={kwargs}")

flexible_function(1, 2, 3, name="Sam", age=30)
# required=1, args=(2, 3), kwargs={'name': 'Sam', 'age': 30}
Real-world example Writing a generic wrapper or decorator function that needs to forward ANY arguments through to the wrapped function unchanged.

Common follow-ups: How do you UNPACK a list and dict back into a function call using * and ** at the CALL site, the reverse operation?

Decorators
All 15 Functions & Scope questions