🎯 Python Function Arguments — Understanding How Data Enters Functions

Introduction 🌟

Function arguments are the values you pass into a function when calling it. Python provides several flexible ways to pass data, making functions powerful and reusable.

Note

💡 Understanding arguments is essential for writing professional, maintainable Python code.

1. Positional Arguments 📌

These arguments are passed **in order**, and the position matters.

positional_args.py

def add(a, b):
    print(a + b)

add(10, 20)  # 30

2. Keyword Arguments 🧩

Arguments passed using the format key=value. Order does NOT matter.

keyword_args.py

def student(name, age):
    print(name, age)

student(age=21, name="Sathish")

Note

✔️ Keyword arguments improve clarity and avoid ordering mistakes.

3. Default Arguments 🧃

Arguments with default values used when no value is provided.

default_args.py

def greet(name="Guest"):
    print("Hello", name)

greet()         # Hello Guest
greet("Kumar")  # Hello Kumar

Note

⚠️ Default arguments must come **after** non-default ones.

4. Arbitrary Positional Arguments (*args) 🔢

Use *args when you don't know how many arguments will be passed. Arguments are received as a tuple.

args_example.py

def add(*nums):
    print(nums)
    print("Sum =", sum(nums))

add(1, 2, 3, 4)

5. Arbitrary Keyword Arguments (**kwargs) 🧰

Use **kwargs to accept multiple named arguments. They are stored in a dictionary.

kwargs_example.py

def display(**info):
    print(info)

display(name="Sathish", age=25, country="India")

6. Keyword-Only Arguments 🛑➡️🧩

Use * to force certain parameters to be keyword-only.

keyword_only.py

def order(item, *, quantity=1, price=0):
    print(item, quantity, price)

order("Book", quantity=2, price=500)
# order("Book", 2, 500)  ❌ Error

Note

✔️ Helps prevent confusion and improves readability.

7. Positional-Only Arguments ( / ) 📐

Introduced in Python 3.8, / forces arguments to be positional-only.

positional_only.py

def divide(a, b, /):
    return a / b

print(divide(10, 2))  
# divide(a=10, b=2)  ❌ Error

8. Combining All Argument Types 🔥

Python allows mixing all styles in a single function.

combined_args.py

def func(a, b=10, *args, c=20, **kwargs):
    print(a, b, args, c, kwargs)

func(1, 2, 3, 4, 5, c=30, x=100, y=200)

Note

✔️ Order must be:positional → default → *args → keyword-only → **kwargs

9. Passing Lists, Tuples, Dicts as Arguments 📦

List

list_arg.py

def total(nums):
    print(sum(nums))

total([1, 2, 3, 4])

Tuple

tuple_arg.py

def show(items):
    for i in items:
        print(i)

show((10, 20, 30))

Dictionary

dict_arg.py

def print_info(info):
    for k, v in info.items():
        print(k, "=", v)

print_info({"name": "Sathish", "age": 25})

10. Argument Unpacking Using * and ** 🎁

unpack_args.py

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

nums = [1, 2, 3]
add(*nums)   # unpack list

info = {"a": 5, "b": 10, "c": 15}
add(**info)  # unpack dictionary

11. Real-World Examples 🌍

Flexible Logging Function

logging.py

def log(message, **data):
    print("LOG:", message)
    for k, v in data.items():
        print(f"{k}: {v}")

log("User login", user="Sathish", status="success")

Billing System

billing.py

def bill(*items):
    total = sum(items)
    return total

print(bill(100, 200, 350))

Dynamic Settings Loader

settings.py

def configure(**settings):
    return settings

print(configure(theme="dark", font="Arial", size=14))

Conclusion 🎉

>>“Mastering arguments gives your functions ultimate flexibility and power.” ✨

You now clearly understand all types of Python function arguments! Want the next topic? Try Lambda Functions, Recursion, Modules, or OOP (Classes & Objects). Just tell me! 😊