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User-Defined Functions
User-defined functions are created by the user according to the need of the program. Once the
user defines a function, the user can call it in the same way as the built-in functions. User-defined
functions are divided into various categories based on the parameters and return type. The
functions that do not take any parameter or return anything are called type 1 functions.
The type 2 functions take parameters but do not return anything. The type 3 functions take
parameters and return output. Let us understand this with the help of an example:
Program 1: To add two numbers using all the three types of built-in functions.
You will get the following output:
Creating a Function
We can create a function in the following ways:
Defining a Function: We use the def keyword to begin the function definition.
Naming a Function: Provide a meaningful name to your function.
Supply Parameters: The parameters (separated by commas) are given in the parenthesis
following the name of the function. These are basically the input values we pass to the function.
Functions, String and List in Python 121

