Python’s *args and **kwargs — The Ultimate Guide with Examples and Interview-Ready Insights

One of Python’s most flexible and readable features is its support for variable-length arguments using *args and **kwargs.

But if you’ve ever wondered:

• What do *args and **kwargs actually mean?
• How do they work under the hood?
• When should you use them — and when shouldn’t you?

You’re in the right place. This guide explains it all, with clear examples, visual breakdowns, and pro tips for interviews and real-world use.

---

🧠 What Are *args and **kwargs?

Syntax	Name	Accepts
*args	Positional arguments	A tuple of unnamed values
**kwargs	Keyword arguments	A dictionary of named values

---

✅ Using *args: Accepting Multiple Positional Arguments

pythonCopyEditdef add(*args):
    return sum(args)

print(add(1, 2, 3))   # ➜ 6
print(add(10, 20))    # ➜ 30

What’s happening:

• args is a tuple: (1, 2, 3)
• You can pass any number of values
• You don’t have to name them

---

✅ Using **kwargs: Accepting Multiple Keyword Arguments

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

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

What’s happening:

• kwargs is a dictionary: {'name': 'Alice', 'age': 30}
• You can pass any named (key=value) arguments

---

📦 Combining *args and **kwargs

Yes, you can use both — and this is where things get powerful:

def log(level, *args, **kwargs):
    print(f"[{level}]")
    print("ARGS:", args)
    print("KWARGS:", kwargs)

log("INFO", 1, 2, a=10, b=20)

✅ Output:

[INFO]
ARGS: (1, 2)
KWARGS: {'a': 10, 'b': 20}

🧠 Order matters: *args must come before **kwargs.

---

🧩 Unpacking with * and ** When Calling Functions

These stars also work in reverse, to unpack data into arguments:

nums = [1, 2, 3]
print(add(*nums))     # ➜ same as add(1, 2, 3)

info = {"name": "Bob", "age": 25}
greet(**info)         # ➜ same as greet(name="Bob", age=25)

---

🧠 Visual Breakdown

def example(fixed, *args, **kwargs):
    ...

Call:

pythonCopyEditexample("Hi", 1, 2, 3, x=10, y=20)

Internally:

fixed   = "Hi"
args    = (1, 2, 3)
kwargs  = {'x': 10, 'y': 20}

---

💼 Real-World Use Cases

Use Case	Why *args / **kwargs Help
Logging / debugging tools	Capture any input flexibly
API wrapper functions	Forward unknown inputs
Class inheritance / override	Accept parent class params
Decorators	Work with arbitrary functions
Config loading	Accept unknown keyword config

---

💡 Interview Questions You Might Hear

❓ “What is the difference between *args and **kwargs?”

✅ *args captures extra positional arguments as a tuple.
✅ **kwargs captures extra keyword arguments as a dictionary.

---

❓ “Can I use both at once?”

Yes, in this order:

def my_func(fixed, *args, **kwargs): ...

---

❓ “Can I forward arguments to another function?”

Yes!

def wrapper(*args, **kwargs):
    return original_func(*args, **kwargs)

---

⚠️ Common Mistakes

• ❌ Using *args after **kwargs — order matters!
• ❌ Assuming args is a list — it’s actually a tuple
• ❌ Confusing unpacking syntax (*/**) for passing vs receiving

---

✅ Summary

Concept	Meaning
*args	Accepts extra positional arguments (tuple)
**kwargs	Accepts extra keyword arguments (dict)
Unpacking	Use * and ** when calling functions
Order	Always: def func(fixed, *args, **kwargs)

---

🏁 Final Thoughts

Python gives you a powerful, elegant way to write flexible functions that can accept any number of arguments. Whether you’re building a logging utility, designing APIs, or writing decorators — mastering *args and **kwargs is essential.

So next time you see a function definition full of stars, you’ll know:

“This function is ready for anything.”