Function In Python: Some Important Points You Should Know

Function In Python

Sometimes, you (as a programmer) notice that you need a particular function or method that you can use for repeated work. Python offers several functions that are easy to use for the user for executing the repeated work. Don’t you know what the function in Python is? 

Well, you do not need to go and search for each function individually. I have detailed all the functions in Python. All these help you to know which function you should use for your work to make it simpler. So, let’s start with today’s topic. But first, let’s see what the functions are.

What are the Python functions?

It is the block of all the related statements created to execute the logical, computational, and evaluative task. Here, the function in Python is used for putting the repeated or commonly done tasks at a place. 

These functions help to save time and prove the readability of the code. You can use the particular function rather than write similar code repeatedly for the different inputs. Whenever you need to repeat a particular task, you can frequently use the function to reuse the same code in it.


def function_name(parameters):



    return expression

Some key points about function in Python

There are some major rules to flow that define the function in Python. And these are:

> The function block should begin the keyword def, and it is followed by the name of the function and parentheses ().

> The function’s first statement can also be the optional statement. And its documentation string must start with the function docstring.

> The function in Python with the return statement (that has no argument) is similar to the return None.

> The parenthesis should include any input arguments or parameters. Within the parenthesis, you can also define arguments.

> Every function’s code block should begin with a colon (:) and also should be indented.

Are there only the user-defined functions?

No, apart from the user-defined functions, there are built-in functions in Python. (For beginners: the functions that the user defines are known as user-defined functions.) 

Each programming language consists of some of the library/pre-defined functions for implementing the basic functionalities. And the most used function is print() that is used for printing a particular message.

But sometimes, you find that language has not defined the function that you need to use for the particular action. In that case, the user defines the function and uses it wherever required.

Note: Why do we use a function in Python?

With the help of the functions, you can refine your Python code’s readability and enhance the reusability of the codes. It means you can use the functions instead of writing a long code. 

Because of the simplicity of the programs, the debugging process becomes quite easier. And you can get the errors with ease. Therefore, using the function is a good idea.

So, how to call the functions into the existing program?

The function can use with its name. And you need to add the valid value to the parameters that are specified at the time of defining the function. 

The syntax for calling the function:


Here, I am taking an example of adding the two numbers. But you will see that one uses the print function, and the other uses the return statement.

Function with the print and return statement

Function In Python


The sum is: 20

NOTE: Here, a and b are taken as the parameters, whereas 5 and 15 are the functions’ arguments.

Function with the print but without return statement

Function In Python



NOTE: The sum() function has returned the output in the given code as the None object for each caller function.

Read: How To Write Better Python Code

How to use arguments of the functions?

First of all, let me clarify that arguments are the value passed within the function’s parenthesis. The function can include various arguments, and each one is separated using the comma (,).

Let’s take an example of it:

Check the number (passed as the argument) and know whether the number is odd or even.

Function In Python




What are the top 3 types of argument function in Python?

Default arguments

It is the parameter considered the default value (but only if the value is not given within the called function). Let’s take an example of it:

Function In Python


x:  15

y:  35

Keyword arguments

Here, the only idea is to allow the callers to define the name of the arguments with the specific value. This will help the caller not to remember the parameters’ order. Example:

Function In Python


Code Avail

Code Avail

Variable-length arguments

Python users can easily pass the argument’s variable number to the specific function with the help of using particular symbols. And those are:

  • **kwargs (Keyword Arguments)
  • *args (Non-Keyword Arguments)

Let’s understand it with some examples:

  • The variable-length argument using non-keywords:
Function In Python






  • The variable-length argument using keywords:
Function In Python


first == Code

last == Avail

Bonus Point:

Is there any function that can be declared without a name?

Yes, there is! The functions that are declared without a name are known as an anonymous function. Now, you already know that you can declare the normal functions using the def keyword. And the anonymous functions can define using the keyword lambda. This is how you can define the anonymous function:



How to define the Python function within another function?

Sometimes, there is a need to define the function within another function. It is possible in Python, and it is called nested or inner function. The nested function can access the enclosing scope’s variables. Now, the inner function uses to protect from everything that is going to happen outside the function.

Function In Python



Final thoughts!

The function in Python plays a key role in Python programs. These are useful when you need to repeat a task. Instead of writing a long code, you can just call the function at the program’s necessary place and use it effectively. 

If you do not have any built-in function, you can define a function on your own and call it in the hour of need. I have defined all the necessary details that you might be thinking of searching for. Now, do not waste your precious time searching for the details. Instead, use it to practice the Python functions (on the different IDEs). 

If you are stuck with the program of Python functions, let me know through your mail. And I will definitely help you with your queries of Python in Python programming help

Remember: CodeAvail is the right choice for you, whether for learning or improving your grades.

Frequently Asked Questions

Which keyword is used for function?

A function in Python is used with the keyword def. And you can also define the function(s) on your own. Those functions are known as user-defined functions.

Where is the function defined?

You can easily define functions within a class, a module, a class, or another function.

Why do we need functions?

There are many reasons for using the functions in Python, and some of those are:

  • improving the code’s readability
  • enhancing the code’s reusability
  • it becomes quite easier to debug the code.