Parameters & Arguments in Python

Parameters and arguments are used to provide data to a function. This allows us to use the same function multiple times with different values.

1. What is a Parameter?

A parameter is a variable used inside the function definition to receive input.

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

In this example, name is a parameter.

2. What is an Argument?

The actual value passed when calling a function is called an argument.

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

greet("Rahul")

Here, name is the parameter and "Rahul" is the argument.

Output:

Hello Rahul

3. Parameter vs Argument

4. Single Parameter

def square(number):
    return number * number

result = square(5)

print(result)

Output:

25

5. Multiple Parameters

You can also define multiple parameters in a function.

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

result = add(10, 20)

print(result)

Output:

30

6. Positional Arguments

In positional arguments, the order of values matches the order of the parameters.

def student(name, course):
    print("Name:", name)
    print("Course:", course)

student("Amit", "Python")

Output:

Name: Amit
Course: Python

7. Keyword Arguments

In keyword arguments, we explicitly specify the parameter name.

def student(name, course):
    print("Name:", name)
    print("Course:", course)

student(
    course="Python",
    name="Amit"
)

Output:

Name: Amit
Course: Python

The benefit of keyword arguments is that even if the order of values changes, the correct value is assigned to the corresponding parameter.

8. Default Parameters

A parameter can be given a default value. If a value is not provided when calling the function, the default value is used.

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

greet()
greet("Rahul")

Output:

Hello Student
Hello Rahul

9. Multiple Default Parameters

def student_info(
    name="Student",
    course="Python"
):
    print("Name:", name)
    print("Course:", course)

student_info()

student_info(
    "Amit",
    "Python Full Stack"
)

Output:

Name: Student
Course: Python

Name: Amit
Course: Python Full Stack

10. Positional + Keyword Arguments

Positional and keyword arguments can be used together.

def student(name, course, city):
    print(name)
    print(course)
    print(city)

student(
    "Rahul",
    course="Python",
    city="Pune"
)

Output:

Rahul
Python
Pune

11. Arbitrary Positional Arguments (*args)

When we do not know how many arguments a function will receive, we can use *args.

def total(*numbers):

    total = 0

    for number in numbers:
        total += number

    return total


print(total(10, 20))
print(total(10, 20, 30, 40))

Output:

30
100

12. Arbitrary Keyword Arguments (**kwargs)

**kwargs can be used to accept multiple keyword arguments.

def student_info(**details):

    for key, value in details.items():
        print(key, ":", value)


student_info(
    name="Amit",
    course="Python",
    city="Pune"
)

Output:

name : Amit
course : Python
city : Pune

13. *args vs **kwargs

14. CIIT Example 👀🤓

We create a function for student enrollment at CIIT.

def enroll_student(name, course, city="Pune"):

    print("Student:", name)
    print("Course:", course)
    print("City:", city)


enroll_student(
    "Sneha",
    "Python Full Stack"
)

Output:

Student: Sneha
Course: Python Full Stack
City: Pune

15. Calculation Example 👀🤓

def calculate_fee(fee, discount):

    final_fee = fee - (fee * discount / 100)

    return final_fee


amount = calculate_fee(35000, 10)

print("Final Fee:", amount)

Output:

Final Fee: 31500.0

16. Common Mistakes

# Wrong
def add(a, b):
    return a + b

add(10)

Here, the value for b is missing, so an error will occur.

# Correct
def add(a, b):
    return a + b

add(10, 20)

17. Important Rules

• Give function parameters meaningful names.
• The order of positional arguments is important.
• Keyword arguments are passed with the parameter name.
• A default parameter provides optional input.
• *args handles multiple positional arguments.
• **kwargs handles multiple keyword arguments.