Calling a Function

Understanding Function Calls in Python

When you are writing code in Python, you’ll often need to use functions to perform various tasks. A function is a block of code with a name that performs a specific task when called. In this article, we will discuss the concept of calling a function, which is an important aspect of programming.

What is a Function Call?

A function call is a statement that executes a function with a specific set of arguments, triggering the function’s code to run. When you call a function, you are essentially instructing the computer to execute a specific set of instructions that are contained within the function.

To call a function in Python, you must first define the function using the def statement. This statement creates a new function object and gives it a name. Then, when you want to use that function, you simply reference it by that name and provide any arguments that it requires.

Calling a Function

To call a function in Python, you simply write the function name followed by parentheses containing any arguments that it requires. Here is an example of a function call in Python:

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


In this example, the greet() function is defined with one parameter called name. When the function is called using greet("John"), the string “John” is passed as an argument to the function. The function then prints the message “Hello, John!”.

Passing Arguments to a Function

When calling a function, you can pass it one or more arguments as needed. These arguments are values that the function needs to perform its task. For example, if you have a function that calculates the area of a rectangle, you would need to pass the length and width of the rectangle as arguments.

To pass arguments to a function, simply list them inside the parentheses when calling the function. Here is an example:

def calculate_area(length, width):
    area = length * width
    print("The area of the rectangle is:", area)

calculate_area(5, 10)

In this example, the calculate_area() function is defined with two parameters called length and width. When the function is called using calculate_area(5, 10), the values 5 and 10 are passed as arguments to the function. The function then calculates the area of the rectangle using the formula length * width, and prints the result.

Returning Values

A function can also return a value, which is a piece of data that can be used by the calling code. For instance, a function that calculates the sum of two numbers could return the result of the calculation to the calling code.

To return a value from a function, use the return keyword followed by the value that you want to return. Here is an example:

def sum_numbers(num1, num2):
    sum = num1 + num2
    return sum

result = sum_numbers(2, 3)
print("The sum is:", result)

In this example, the sum_numbers() function takes two numbers as arguments, adds them together, and returns the sum using the return keyword. When the function is called with arguments 2 and 3, it returns the value 5. This value is then assigned to the variable result, which is printed to the console.


In conclusion, calling a function is an essential part of Python programming. By calling functions, we can reuse code, make our programs more organized, and make our code more readable. Now that you have a better understanding of how function calls work in Python, you can use them to create more efficient and effective programs.

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