In what situations is it appropriate to use *args when defining a function in Python?

*args in Python is used when you need to define a function that can accept a variable number of positional arguments. This is convenient if the exact number of arguments is unknown in advance, or if the function should handle an arbitrary set of parameters.

Example of usage:

def summa(*args):
    total = 0
    for num in args:
        total += num
    return total

print(summa(1, 2, 3))  # Outputs 6
print(summa(5, 10))    # Outputs 15

Thus, *args is useful for creating flexible functions that can work with a different number of input data.