Defining Function

With Return

C/C++/Java

int add() {
	int a = 20;
	int b = 40;
    int c = a + b
    return c;
}

Python

def add():
    a = 20
    b = 40
    c = a + b
    return c

• return_type: The data type of the value the function will return (e.g., int, float, void for no return).
• function_name: The name of the function.
• parameters: The input variables or arguments passed to the function (optional).

Without Return

C/C++/Java

void greeting() {
    printf("Hi there!\n");
}

Python

def greeting():
    print("Hi there!")

• Without return means when the function is called, it won’t return any value. Instead, it will only execute the commands inside. For example: printing a sentence.

Example

Without Parameter

C / C++ / Java

void greet() {
	// in C
    printf("Hello, welcome!\n");

	// in C++
    std::cout << "Hello, welcome!" << std::endl;

    // in Java
    System.out.println("Hello, welcome!");
}

int main() {
    // Calling the function
    greet(); // Function call
    return 0;
}

Python

def greet():
    print("Hello, welcome!")
greet()

Output:

"Hello, welcome"

Note:

• In C and C++, the functions need to be defined b__efore the main function__.
• In Java, it's not necessary to define the functions before the main function.
• Since Python is an interpreted language, there's no need for a separate main() function. The script is executed sequentially, and code outside functions is executed when the script is run. Therefore, the greet() function is called directly.

With Parameter

C / C++ / Java

int addNumbers(int a, int b) {
    int sum = a + b;
    return sum;
}

int main() {
    int num1 = 5;
    int num2 = 3;
    int result = addNumbers(num1, num2);

    printf("The sum of %d and %d is: %d\n", num1, num2, result);
    return 0;
}

Python

def add_numbers(a, b):
    sum = a + b
    return sum

num1 = 5
num2 = 3
result = add_numbers(num1, num2)

print(f"The sum of {num1} and {num2} is: {result}")

Output:

“The sum of 5 and 3 is: 8”

Note:

• In Python, the script is executed sequentially, and code outside functions is run when the script is executed. Therefore, you can directly call the function without encapsulating the logic within a specific main function.

Challenge:

• try to print the sum variable inside the main function, can you see the output? C / C++ / Java
• try to print the sum variable outside of the add_numbers() function, can you see the output ? Python