Keyword arguments in Python

Introduction

Keyword arguments let you give values to a function by naming them. This makes your code easier to read and understand.

When a function has many inputs and you want to be clear about which value goes where.

When you want to skip some optional inputs and only set specific ones.

When you want to avoid mistakes by mixing up the order of inputs.

When you want to make your code easier to read for others or yourself later.

Syntax

Python

def function_name(param1=value1, param2=value2):
    # function body

function_name(param1=valueA, param2=valueB)

You write the parameter name followed by an equal sign and the value.

Order does not matter when calling with keyword arguments.

Examples

Here, we call the function using keyword arguments to clearly show which value is for which parameter.

Python

def greet(name, age):
    print(f"Hello {name}, you are {age} years old.")

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

We use a default value for animal_type and only provide pet_name as a keyword argument.

Python

def describe_pet(pet_name, animal_type='dog'):
    print(f"I have a {animal_type} named {pet_name}.")

describe_pet(pet_name='Buddy')

Keyword arguments let us give values in any order.

Python

def order_food(main, side, drink):
    print(f"Main: {main}, Side: {side}, Drink: {drink}")

order_food(drink='Water', main='Burger', side='Fries')

Sample Program

This program shows how keyword arguments make it easy to call the function without worrying about the order of inputs.

Python

def book_flight(destination, date, seat_class='Economy'):
    print(f"Booking a {seat_class} seat to {destination} on {date}.")

book_flight(date='2024-07-01', destination='Paris')
book_flight(destination='Tokyo', date='2024-08-15', seat_class='Business')

Important Notes

You can mix positional and keyword arguments, but positional ones must come first.

Using keyword arguments improves code readability and reduces errors.

Summary

Keyword arguments let you name inputs when calling a function.

They make your code clearer and easier to understand.

You can give values in any order when using keyword arguments.

Practice

1. What is the main advantage of using keyword arguments when calling a function in Python?

easy

A. Keyword arguments make the function run faster.

B. You must provide arguments in the exact order defined in the function.

C. You can specify arguments by name, making the code clearer.

D. They allow you to skip required arguments.

Solution

1. Step 1: Understand keyword arguments

   Keyword arguments let you name the inputs when calling a function, so you don't have to remember the order.

2. Step 2: Compare options

   You can specify arguments by name, making the code clearer. correctly states that naming arguments makes code clearer. Options B, C, and D are incorrect because keyword arguments do not require order, do not affect speed, and cannot skip required arguments.

3. Final Answer:

   You can specify arguments by name, making the code clearer. -> Option C

4. Quick Check:

   Keyword arguments = clearer code [OK]

Hint: Keyword arguments name inputs, so order doesn't matter [OK]

Common Mistakes:

• Thinking keyword arguments must follow positional order
• Believing keyword arguments speed up the function
• Assuming keyword arguments can skip required parameters

2. Which of the following is the correct way to call the function def greet(name, age): using keyword arguments?

easy

A. greet(name='Alice', age=30)

B. greet('Alice', 30)

C. greet(age=30, 'Alice')

D. greet(name=30, age='Alice')

Solution

1. Step 1: Check keyword argument syntax

   Keyword arguments require the format parameter=value. greet(name='Alice', age=30) uses name='Alice' and age=30, which is correct.

2. Step 2: Identify errors in other options

   greet('Alice', 30) uses positional arguments only, which is valid syntax but does not use keyword arguments. greet(age=30, 'Alice') places positional argument after keyword, which is invalid syntax. greet(name=30, age='Alice') swaps types incorrectly.

3. Final Answer:

   greet(name='Alice', age=30) -> Option A

4. Quick Check:

   Keyword args = parameter=value pairs [OK]

Hint: Use parameter=value pairs for keyword arguments [OK]

Common Mistakes:

• Placing positional arguments after keyword arguments
• Swapping argument names and values
• Mixing types incorrectly in keyword arguments

3. What will be the output of the following code?

def info(name, age):
    print(f"Name: {name}, Age: {age}")

info(age=25, name='Bob')

medium

A. Name: 25, Age: Bob

B. Name: Bob, Age: 25

C. Name: , Age:

D. TypeError

Solution

1. Step 1: Understand keyword argument order

   Keyword arguments allow passing arguments in any order by naming them explicitly.

2. Step 2: Match arguments to parameters

   Here, age=25 and name='Bob' are passed, so name gets 'Bob' and age gets 25.

3. Final Answer:

   Name: Bob, Age: 25 -> Option B

4. Quick Check:

   Keyword args reorder inputs correctly [OK]

Hint: Keyword arguments can be in any order [OK]

Common Mistakes:

• Assuming order matters with keyword arguments
• Confusing parameter names with values
• Expecting errors when order is changed

4. Identify the error in the following function call:

def multiply(x, y):
    return x * y

result = multiply(x=5, 10)

medium

A. SyntaxError: positional argument after keyword argument

B. TypeError: missing required positional argument

C. No error, result is 50

D. NameError: variable not defined

Solution

1. Step 1: Check argument order rules

   In Python, positional arguments cannot come after keyword arguments in a function call.

2. Step 2: Analyze the call

   The call multiply(x=5, 10) has a keyword argument first, then a positional argument, which causes a syntax error.

3. Final Answer:

   SyntaxError: positional argument after keyword argument -> Option A

4. Quick Check:

   Positional args must come before keyword args [OK]

Hint: Positional arguments must come before keyword arguments [OK]

Common Mistakes:

• Placing positional arguments after keyword arguments
• Confusing error types for this syntax
• Assuming this call runs without error

5. Given the function def order(item, quantity=1, price=10):, which call correctly orders 3 items with a price of 15 each using keyword arguments?

hard

A. order('apple', 3, 15)

B. order(price=15, quantity=3)

C. order(quantity=3, 'apple', price=15)

D. order(item='apple', price=15, quantity=3)

Solution

1. Step 1: Understand function parameters and defaults

   The function has one required parameter item and two optional parameters quantity and price with defaults.

2. Step 2: Check each call for correctness

   order('apple', 3, 15) uses positional arguments only, which is valid but not keyword arguments. order(item='apple', price=15, quantity=3) uses keyword arguments for all parameters, correctly naming them in any order. order(quantity=3, 'apple', price=15) places positional argument after keyword argument, which is invalid. order(price=15, quantity=3) misses the required item argument.

3. Final Answer:

   order(item='apple', price=15, quantity=3) -> Option D

4. Quick Check:

   Keyword args can be in any order, all required given [OK]

Hint: Use all required keywords, order doesn't matter [OK]

Common Mistakes:

• Omitting required arguments
• Placing positional after keyword arguments
• Using positional only when keyword is asked