🐍 args & kwargs

arguments

Good to know

⭐ args* collects any number of positional arguments into a tuple. ⭐ kwargs collects any number of named arguments into a dictionary. ⭐ Both are useful when you don’t know how many values a function will receive.

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Using args (Positional Arguments)

args collects extra values into a tuple.

def add(*args):
    print(args)         # ('a', 'b', 'c')
    return sum(args)
 
add(1, 2, 3)
# → 6

Looping Through args

Useful for dynamic aggregations.

def print_all(*args):
    for item in args:
        print(item)
 
print_all("Jim", "Tom", 42)

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Using kwargs (Keyword Arguments)

kwargs collects named arguments into a dictionary.

def show_info(**kwargs):
    print(kwargs)        # {'name': 'Alain', 'age': 33}
 
show_info(name="Alain", age=33)

Looping Through kwargs

Get both the key and the value.

def show_info(**kwargs):
    for key, value in kwargs.items():
        print(key, value)
 
show_info(first="Sir", middle="Alain", last="Haldi")

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Combining args and kwargs

Order matters: *args always comes before **kwargs.

def demo(a, b, *args, **kwargs):
    print(a, b)
    print(args)          # extra positional values
    print(kwargs)        # extra named values
 
demo(1, 2, 3, 4, x=10, y=20)

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Passing a List or Dict Into a Function

You can unpack values when calling a function.

Unpack list → *args

def total(a, b, c):
    return a + b + c
 
values = [1, 2, 3]
print(total(*values))     # same as total(1, 2, 3)

Unpack dict → **kwargs

def greet(name, title):
    print(title, name)
 
person = {"name": "Alain", "title": "Mr."}
greet(**person)            # same as greet(name="Alain", title="Mr.")

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Real-World Example: Flexible Logging Function

def log(message, **data):
    print(message)
    for key, value in data.items():
        print(f" - {key}: {value}")
 
log("User login", user="Alain", ip="127.0.0.1", success=True)