REFERENCEpython

python Documentation

📖 INDEX

# print

# arithmetic-operators

# assignment-operators

# comparison-operators

# logical-operators

# identity-operators

# membership-operators

# keyword-arguments-kwargs

# default-parameter-value

# class-methods-classmethod

# static-methods-staticmethod

# dunder-methods

# try-block

# except-block

# else-block-exceptions

# list-comprehensions

# dictionary-comprehensions

# set-comprehensions

# iterators

# property-decorator-property

# context-managers-contextmanager

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Keyword Arguments (**kwargs)

AI & DATA SCIENCE // keyword-arguments-kwargs

**kwargs collects any number of extra keyword arguments passed to a function into a dictionary, letting the function accept arbitrary named inputs.

Syntax

def func(**kwargs):
    for key, value in kwargs.items():
        ...

func(a=1, b=2)

Deep Dive Course

A parameter prefixed with a double asterisk gathers every keyword argument the caller passes that doesn't match a named parameter, collecting them into a dict keyed by argument name — again, kwargs is just a conventional name. This is how functions can accept flexible, optional configuration without listing every possible option explicitly, and it's often paired with *args to build fully generic wrapper functions and decorators. At a call site, the double asterisk unpacks an existing dict into separate keyword arguments.

1Understanding Keyword Arguments (**kwargs)

💡

Use a double asterisk at a call site to spread an existing dictionary out into keyword arguments — the mirror image of collecting them with **kwargs in a function definition, and a common pattern for forwarding configuration through a chain of function calls.

editor.html

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

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

localhost:3000

2Practical Example

Here is a real-world application of Keyword Arguments (kwargs)** showing how it is used in production Python code.

editor.html

def build_url(base, **params):
    query = "&".join(f"{k}={v}" for k, v in params.items())
    return f"{base}?{query}"

print(build_url("/search", q="python", page=2))

localhost:3000

3Best Practices

Follow these guidelines when working with Keyword Arguments (kwargs)**:

1. Use **kwargs when a function needs to accept flexible, optional named configuration it doesn't fully know in advance

2. Prefer explicit named parameters with defaults over **kwargs when the accepted options are actually fixed and known

3. Combine *args and **kwargs in wrapper functions/decorators to forward arbitrary arguments through to the wrapped function unchanged

⚠️

Tip: Use a double asterisk at a call site to spread an existing dictionary out into keyword arguments — the mirror image of collecting them with **kwargs in a function definition, and a common pattern for forwarding configuration through a chain of function calls.

editor.html

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

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

localhost:3000

Examples

Example 01Basic Usage

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

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

Example 02Advanced Example

def build_url(base, **params):
    query = "&".join(f"{k}={v}" for k, v in params.items())
    return f"{base}?{query}"

print(build_url("/search", q="python", page=2))

Best Practices

Use **kwargs when a function needs to accept flexible, optional named configuration it doesn't fully know in advance
Prefer explicit named parameters with defaults over **kwargs when the accepted options are actually fixed and known
Combine *args and **kwargs in wrapper functions/decorators to forward arbitrary arguments through to the wrapped function unchanged

Interview Question

How would you write a generic decorator that works on any function, regardless of what arguments it takes?▼

Hint: Think about combining *args and **kwargs.

Define the wrapper function to accept *args and **kwargs itself, then forward both straight through to the wrapped function's call, unpacking them back into a normal call. Because *args captures any positional arguments and **kwargs captures any keyword arguments, the wrapper works regardless of the wrapped function's actual signature, which is exactly why this pattern is standard for writing general-purpose decorators.

Exercises

MediumPractice using Keyword Arguments (**kwargs) in a real scenario.

View Solution

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

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

Frequently Asked Questions

How would you write a generic decorator that works on any function, regardless of what arguments it takes?▼

Related Functions

arguments-argsdecoratorsdictionaries