Python Tip: *args and **kwargs

Create flexible functions with variable arguments

Learn how to create flexible functions that accept any number of arguments using *args and **kwargs.

Author

Shep Bryan IV

Python Tip: `*args` and `**kwargs`

Python makes it easy to create functions that can take any number of arguments. Use *args and **kwargs for flexible and reusable code.

Understanding `*` and `**`

Before diving into *args and **kwargs, let’s understand the * and ** operators.

The single asterisk (*) unpacks iterables like lists. The double asterisk (**) unpacks dictionaries.

# Single asterisk (*) unpacks an iterable
list1 = [1, 2, 3]
list2 = [4, 5, 6]

list3_with_unpacking = [*list1, *list2]
list3_without_unpacking = [list1, list2]

print(list3_with_unpacking)     # [1, 2, 3, 4, 5, 6]
print(list3_without_unpacking)  # [[1, 2, 3], [4, 5, 6]]

[1, 2, 3, 4, 5, 6]
[[1, 2, 3], [4, 5, 6]]

# Double asterisk (**) unpacks dictionaries
dict1 = {"a": 1, "b": 2}
dict2 = {"c": 3, "d": 4}

dict3_with_unpacking = {**dict1, **dict2}
print(dict3_with_unpacking)  # {'a': 1, 'b': 2, 'c': 3, 'd': 4}

{'a': 1, 'b': 2, 'c': 3, 'd': 4}

Using `*args` for Variable Arguments

When asterisks are used in function definitions, they pack arguments into tuples.

def average(*args):  # args=(arg1, arg2, arg3, ...)
    return sum(args) / len(args)

result = average(1, 2, 3, 4, 5)
print(result)  # 3.0

3.0

By packing arguments into a tuple, you can pass any number of arguments to the function.

Using `**kwargs` for Keyword Arguments

When double asterisks are used in function definitions, they pack keyword arguments into dictionaries.

def greet(**kwargs):
    for key, value in kwargs.items():
        print(f"{key}: {value}")

greet(name="Alice", age=30)

name: Alice
age: 30

**kwargs allows you to pass named arguments without explicitly defining each one.

Combining `*args` and `**kwargs`

You can use both *args and **kwargs in the same function. Important: *args must appear before **kwargs.

def show_info(*args, **kwargs):
    print("Positional arguments:", args)
    print("Keyword arguments:", kwargs)

show_info(1, 2, 3, name="Alice", job="Engineer")

Positional arguments: (1, 2, 3)
Keyword arguments: {'name': 'Alice', 'job': 'Engineer'}

Wrap-Up

Now you can create functions that handle any number of positional and keyword arguments, making your code more flexible and reusable.

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Shep Bryan IV

Python Tip: *args and **kwargs

Understanding * and **

Using *args for Variable Arguments