What are *args and **kwargs in Python function definitions?

*args and **kwargs are conventions (the names are arbitrary; the stars are what matter) for writing functions that accept a variable number of arguments.

def log(level, *messages, separator='|', **meta):
    joined = separator.join(messages)
    extra  = ', '.join(f'{k}={v}' for k, v in meta.items())
    print(f'[{level}] {joined}  ({extra})')

log('INFO', 'Server started', 'Listening on port 8080',
    separator=' — ', host='localhost', port=8080)
# [INFO] Server started — Listening on port 8080  (host=localhost, port=8080)

*args collects any extra positional arguments beyond the explicitly named ones into a tuple. **kwargs collects any extra keyword arguments into a dict. Both are optional — you can use either, both, or neither.

The same syntax works on the call side to unpack sequences and mappings:

def add(a, b, c):
    return a + b + c

nums   = [1, 2, 3]
config = {'a': 10, 'b': 20, 'c': 30}

print(add(*nums))      # 6  — unpacks the list
print(add(**config))   # 60 — unpacks the dict as keyword args

A common use case is writing wrapper or decorator functions that forward all arguments to an inner function without knowing what those arguments are. The canonical pattern is def wrapper(*args, **kwargs): return original(*args, **kwargs).

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