How to Call a Function in Python

Last Updated on October 18, 2023 by Ankit Kochar

Calling function in Python is a fundamental concept. Functions are reusable blocks of code that allow you to perform specific tasks, making your code more organized, modular, and easier to maintain. When you call a function, you’re instructing Python to execute the code within that function, often with specific arguments to customize its behavior.

In this article, we’ll explore the ins and outs of calling functions in Python. We’ll cover how to define and call your own functions, use built-in Python functions, pass arguments, and handle return values. Whether you’re a beginner learning the basics of Python or an experienced developer looking to deepen your understanding, this article will provide valuable insights into one of the core concepts of Python programming.

Function in Python

In Python, a function is a block of code that performs a specific task and can be called multiple times from different parts of a program. Functions play a critical role in writing efficient, modular, and reusable code.

To define a function in Python, use the def keyword followed by the name of the function, a set of parentheses, and a colon. The code block of the function is indented below the definition.

Here is an example of a simple function that takes two arguments and returns their sum:

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

result = add_numbers(2, 3)
print(result)

To call a function, simply use its name followed by the arguments in parentheses. Here’s an example of how to call the add_numbers function:

Functions can also have default values for their arguments, which makes them optional. Functions can also return values using the return keyword. This allows the function to pass data back to the calling code.

How to call a Function in Python?

In Python, a function is a block of code that performs a specific task. Functions can take input, process it, and return output. Now we will discuss how to call a function in python, So To call a function in Python, you simply use the function name followed by parentheses and any necessary arguments or parameters inside the parentheses.

When a function is called, the code inside the function is executed. Any input arguments are passed into the function, and the function can use these arguments to perform its task. If the function returns a value, this can be captured and used in the calling code.

Functions in Python can also have default parameters, which are used if an argument is not specified when the function is called. In addition, named parameters can be used to specify arguments by name, rather than position. Let’s have a look at some examples on how to call a function in Python.

Examples to Call a Function in Python

Here are some examples to call a function in python

Example 1: Calling a Function in Python
In this example we simply define a function and call it

Code Implementation:

def f1():
    return "Welcome in Prepbytes"
print(f1())

Output:

Welcome in Prepbytes

Explanation
In the above python program we simply create a function f1 which return a string and we here call this f1 function in print function which simply print the string which returns by the f1 function

Example 2: Calling Nested Function
We can also create and call nested functions; simply create the nested function within the main function and call it in the main function to execute it.

def mainFunc():
    print("We are in the main function")

    def nestedFunc():
        print("This is nested function ")
    
    nestedFunc()

mainFunc()

Output:

We are in the main function
This is nested function

Explanation
In this example, we are defining the main function as well as a nested function within it. We can simply call the nested function from within the main function definition to execute it.

Example 3: Passing Arguments
In this example, we are passing two numbers, subtracting them, and printing the results.

Code Implementation:

def subtraction(a, b):
    print(a-b)

subtraction(20, 8)

Output

12

Explanation
In this above python program we call the function name subtraction and here we pass the argument (20,8) and we got our answer 8 on the output screen.

Example 4: Handling Return Values
In this example we Instead of printing, we return the subtracted value from the arguments and store it in a variable in this example.

Code Implementation:

def subtraction(a, b):
    return a-b

sub = subtraction(20, 5)
print(sub)

Output:

15

Explanation
In the above python program we instead of printing, we return the subtracted value and store it in a variable so here 20 and 5 gives 15 after subtraction which store in sub variable and after this we simply use the print function to print sub variable

Note: Some Python functions do not have a return value. The inbuilt print() function, for example, has no return value and simply prints the arguments to the Python console.

Conclusion
Calling a function in Python is an essential skill that lies at the heart of programming in this versatile language. Functions allow you to encapsulate and reuse code, promoting modularity and readability in your programs. By understanding how to define, call, and work with functions, you can write more efficient, maintainable, and organized Python code.

As you continue your journey with Python, remember that functions are your allies in solving complex problems and building robust applications. They allow you to break down tasks into manageable units of work and facilitate code reuse, ultimately making you a more proficient Python programmer.

In summary, calling functions in Python is not just a fundamental concept; it’s a powerful tool that empowers you to create elegant and efficient solutions to a wide range of problems.

Frequently Asked Questions(FAQ) Related to how to call a function in Python

Here are some FAQs related to how to call a function in Python.

1. How do I call a built-in Python function?
To call a built-in Python function, simply use the function name followed by parentheses and any required arguments. For example, to call the print() function, you would write print("Hello, world!").

2. What is a function argument, and how do I pass arguments to a function?
A function argument is a value that you pass to a function to customize its behavior. To pass arguments to a function, include them within the parentheses when calling the function. For instance, my_function(arg1, arg2).

3. What is the difference between a function parameter and an argument?
A function parameter is a variable defined in the function’s definition, while an argument is a value passed to the function when it’s called. Parameters receive arguments, and they are used within the function to perform operations.

4. What is the difference between local and global variables in Python functions?
Local variables are defined within a function and are only accessible inside that function. Global variables, on the other hand, are defined outside of any function and can be accessed from anywhere in the program.

5. What is function recursion, and when should I use it?
Function recursion is a technique where a function calls itself. It’s commonly used for solving problems that can be broken down into smaller, similar sub-problems, such as computing factorials or Fibonacci numbers.

6. What are lambda functions, and how are they used in Python?
Lambda functions, also known as anonymous functions, are small, unnamed functions defined using the lambda keyword. They are often used for simple, one-time operations and are commonly seen in functions like map(), filter(), and sorted().