Keyword Arguments

What Will You Learn
This tutorial teaches you how to use keyword arguments in Python functions to make your code more readable and maintainable. You’ll understand the difference between positional and keyword arguments, how to specify default values, and why keyword-based calls improve clarity. This concept is essential for writing functions that are easy to understand and use in real projects.

Understanding how to use keyword arguments is a key milestone in mastering function calls. As a beginner, you often start with positional arguments and use them in order. However, this approach quickly becomes limiting once functions grow more complex or take multiple optional parameters. Keyword arguments provide a more flexible and readable way to call functions. They improve clarity, allow default values, and help prevent subtle bugs.

If you're building real-world applications, especially in data science, web frameworks, or automation scripts — keyword arguments appear everywhere. They also make your code more maintainable and explicit. Mastering them early gives you a solid foundation to work with any well-structured codebase. Learning how to use them properly helps you write functions that are easier to understand, test, and reuse.

What Are Keyword Arguments in Python?

Keyword arguments are named parameters you pass to a function by explicitly stating which variable you're assigning a value to. Unlike positional arguments, which rely on order, keyword arguments associate values with parameter names. This makes the function call more readable and less error-prone. They are especially useful when functions have multiple optional parameters. By using them, you can skip some parameters and still provide values for others. You define default values in the function definition to make parameters optional. During the function call, you override only the ones you need. Keyword arguments are passed after positional ones in a function call. Mixing both types correctly is critical to avoid syntax errors.

Example:

    def create_user(name, age=30, role="user"):
        print(f"{name} is {age} years old and has the role '{role}'")

    # Using keyword arguments
    create_user(name="Alice", role="admin")

Explanation:

1. Function Definition:

• This function is called create_user.
• It expects one required parameter (name) and two optional parameters (age, role) with default values.
• If the caller does not provide age or role, Python will use the default values: age=30, role="user".

2. Function Call Using Keyword Arguments:

• This call uses keyword arguments to clearly specify values for name and role.
• It assigns "Alice" to name, and "admin" to role.
• age is not specified, so Python uses the default value: 30.

3. Output:

• The function prints a formatted string using the provided and default values. Output: Alice is 30 years old and has the role 'admin'

What Are the Differences Between Positional and Keyword Arguments in Python?

Positional and keyword arguments are two distinct ways to pass values into functions. Positional arguments are assigned to parameters based on their order in the function call. Keyword arguments, on the other hand, explicitly specify which parameter the value belongs to. This distinction improves readability and minimizes accidental mistakes. You can combine both types in one function call, but positional arguments must always come first. Keyword arguments are ideal when working with functions that accept many optional parameters.

Below is a detailed comparison:

How to Use Keyword Arguments in Python?

Using keyword arguments is straightforward. When calling a function, you assign values by naming the parameters explicitly. This makes the function call clear and often more robust. Keyword arguments are usually used when the function has optional parameters with default values. They can also be used to override only specific parameters, leaving the rest as default.

You must always place keyword arguments after positional ones.

Examples of how to use keyword arguments:

• Call functions with named parameters.
• Improve readability in long argument lists.
• Skip default parameters you don’t want to change.
• Use them with functions that accept **kwargs.
• Avoid bugs caused by incorrect parameter order.
• Document code better by showing parameter meaning.
• Support optional features in flexible APIs.

Advantages of Using Keyword Arguments

Keyword arguments offer several advantages that make them a preferred choice in many scenarios. They enhance code readability, reduce the likelihood of errors, and provide flexibility in function calls. Below are some key benefits:

• Improved Readability: By explicitly naming parameters, the purpose of each argument becomes clear.
• Flexibility: You can skip optional parameters and only specify the ones you need.
• Default Values: Functions can define default values for parameters, making them optional in calls.
• Error Prevention: Reduces the risk of passing arguments in the wrong order.

Example:

        def schedule_meeting(day, time="10:00 AM", duration=1):
                print(f"Meeting scheduled on {day} at {time} for {duration} hour(s)")

        # Using keyword arguments
        schedule_meeting(day="Monday", duration=2)

Combining Positional and Keyword Arguments

You can combine positional and keyword arguments in a single function call. However, positional arguments must always precede keyword arguments. This ensures clarity and avoids ambiguity in parameter mapping.

Example:

        def order_item(item, quantity=1, price=None):
                print(f"Ordered {quantity}x {item} at ${price if price else 'N/A'} each")

        # Combining positional and keyword arguments
        order_item("Laptop", price=999.99)

Using **kwargs for Dynamic Keyword Arguments

The **kwargs syntax allows you to pass a variable number of keyword arguments to a function. These arguments are captured as a dictionary, enabling dynamic and flexible function calls.

Example:

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

        # Passing dynamic keyword arguments
        configure_settings(theme="dark", font_size=12, auto_save=True)

Beginner Mistakes

Mistake 1: Mixing keyword and positional arguments in the wrong order

A common mistake is placing a keyword argument before a positional argument in a function call. This leads to a SyntaxError. Python requires all positional arguments to appear before any keyword arguments. Ignoring this rule causes the interpreter to stop execution and display an error.

Incorrect:

    def greet(name, message):
        print(f"{message}, {name}")

    greet(message="Hi", "Alice")

Correct:

greet("Alice", message="Hi")

Mistake 2: Misspelling parameter names

When using keyword arguments, the parameter names must match exactly those defined in the function signature. Misspelling even a single character will raise a TypeError, stating that an unexpected keyword argument was provided.

Incorrect:

    def register_user(username, email):
        print(f"User: {username}, Email: {email}")

    register_user(usernme="john_doe", email="This email address is being protected from spambots. You need JavaScript enabled to view it.")  

Correct:

register_user(username="john_doe", email="This email address is being protected from spambots. You need JavaScript enabled to view it.")

Mistake 3: Repeating the same argument

You cannot pass the same parameter both positionally and by keyword in the same function call. Doing so results in a TypeError, because Python doesn’t know which value to use.

Incorrect:

    def display(item, price):
        print(f"{item} costs {price}")

    display("Book", item="Notebook")  

Correct:

display(item="Notebook", price=9.99)

Mistake 4: Using undeclared keyword arguments

Passing a keyword that is not listed in the function signature leads to a TypeError. If the function is not designed to accept arbitrary keywords via **kwargs, any unrecognized argument will fail.

Incorrect:

    def add_product(name, quantity):
        print(f"{quantity}x {name}")

    add_product(name="Pen", quantity=10, price=5.99)

Correct:

    def add_product(name, quantity, **kwargs):
        print(f"{quantity}x {name}")
        if "price" in kwargs:
            print(f"Each costs {kwargs['price']}")

Mistake 5: Overcomplicating simple calls

Sometimes beginners overuse keyword arguments even when they’re not necessary. This leads to verbose and harder-to-read code. Use keyword arguments for clarity, not when they make the code harder to scan.

Inefficient:

    def calculate(a, b):
        return a + b

    result = calculate(a=5, b=10)

Better:

result = calculate(5, 10)

Use keywords when function calls benefit from named parameters, especially with optional or out-of-order values.

Frequently Asked Questions

    def describe(name, age):
        print(f"{name} is {age} years old")

    # Positional
    describe("Alice", 30)

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

    def greet(name):
        print(f"Hello, {name}")
    
    greet(username="Alice")  # Error: unexpected keyword

    def greet(name):
        print(f"Hello, {name}")
    
    greet(name="Alice")  # Correct keyword

    def send_email(to, subject="No Subject", priority="normal"):
        print(f"Sending to: {to}, Subject: {subject}, Priority: {priority}")

    def config(**settings):
        for key, value in settings.items():
            print(f"{key} = {value}")
    
    config(theme="dark", timeout=60, retries=3, verbose=True)

    def create_account(username, role="user"):
        print(f"{username} registered as {role}")
    
    # Valid
    create_account("john_doe", role="admin")
    
    # Invalid
    create_account(role="admin", "john_doe")  # SyntaxError

    def log_event(event_type, **details):
        print(f"Event: {event_type}")
        for key, value in details.items():
            print(f"{key}: {value}")
    
    log_event("login", user="Alice", success=True, ip="192.168.0.1")