What is function in python and its types?

Question

Types of Functions in Python: As we have discussed Functions in detail with examples in our previous article. Now we will discuss Types of Functions in Python. There are two types of Function in Python Programming:

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Types of functions
1). Built-in Functions:
Built-in Functions used in Python
2). User-Defined Functions:
What is a function in Python?
Syntax of Function
Example of a function
How to call a function in python?
The return statement
Syntax of return
Example of return
How Function works in Python?
Scope and Lifetime of variables
Types of Functions
What are the 4 types of functions in Python?
What are the main types of functions in Python?
What are functions in Python?
How many types of functions are available in Python?

Types of functions

Types of Functions in Python: There are two types of functions available in python. These are:

Built-in Functions or Pre-defined
User-defined Functions

1). Built-in Functions:

Built-in functions are the functions that are already written or defined in python. We only need to remember the names of built-in functions and the parameters used in the functions. As these functions are already defined so we do not need to define these functions. Below are some built-in functions of Python.

Built-in Functions used in Python

Function name	Description
len()	It returns the length of an object/value.
list()	It returns a list.
max()	It is used to return maximum value from a sequence (list,sets) etc.
min()	It is used to return minimum value from a sequence (list,sets) etc.
open()	It is used to open a file.
print()	It is used to print statement.
str()	It is used to return string object/value.
sum()	It is used to sum the values inside sequence.
type()	It is used to return the type of object.
tuple()	It is used to return a tuple.

More built in functions…

Let’s see one example of built-in functions

#In built functions

x = [1,2,3,4,5]
print(len(x))    #it return length of list
print(type(x))   #it return object type

Output:

# 5                                                                                                                             
# <class 'list'>

2). User-Defined Functions:

The functions defined by a programmer to reduce the complexity of big problems and to use that function according to their need. This type of functions is called user-defined functions.

Example of user-defined functions:

#Example of user defined function

x = 3
y = 4
def add():
    print(x+y)
    
add()

Output:

# 7

Note: User-defined functions are used commonly when we build large projects or applications in our upcoming articles. It is good practice to define functions for larger problems so that our code will remain combined.

What is a function in Python?

In Python, a function is a group of related statements that performs a specific task.

Functions help break our program into smaller and modular chunks. As our program grows larger and larger, functions make it more organized and manageable.

Furthermore, it avoids repetition and makes the code reusable.

Syntax of Function

def function_name(parameters):
	"""docstring"""
	statement(s)

Above shown is a function definition that consists of the following components.

Keyword def that marks the start of the function header.
A function name to uniquely identify the function. Function naming follows the same rules of writing identifiers in Python.
Parameters (arguments) through which we pass values to a function. They are optional.
A colon (:) to mark the end of the function header.
Optional documentation string (docstring) to describe what the function does.
One or more valid python statements that make up the function body. Statements must have the same indentation level (usually 4 spaces).
An optional return statement to return a value from the function.

Example of a function

def greet(name):
    """
    This function greets to
    the person passed in as
    a parameter
    """
    print("Hello, " + name + ". Good morning!")

How to call a function in python?

Once we have defined a function, we can call it from another function, program, or even the Python prompt. To call a function we simply type the function name with appropriate parameters.

>>> greet('Paul')
Hello, Paul. Good morning!

Try running the above code in the Python program with the function definition to see the output.

def greet(name):
    """
    This function greets to
    the person passed in as
    a parameter
    """
    print("Hello, " + name + ". Good morning!")

greet('Paul')

Note: In python, the function definition should always be present before the function call. Otherwise, we will get an error. For example,

# function call
greet('Paul')

# function definition
def greet(name):
    """
    This function greets to
    the person passed in as
    a parameter
    """
    print("Hello, " + name + ". Good morning!")

# Error: name 'greet' is not defined

Docstrings

The first string after the function header is called the docstring and is short for documentation string. It is briefly used to explain what a function does.

Although optional, documentation is a good programming practice. Unless you can remember what you had for dinner last week, always document your code.

In the above example, we have a docstring immediately below the function header. We generally use triple quotes so that docstring can extend up to multiple lines. This string is available to us as the __doc__ attribute of the function.

For example:

Try running the following into the Python shell to see the output.

>>> print(greet.__doc__)

    This function greets to
    the person passed in as
    a parameter

To learn more about docstrings in Python, visit Python Docstrings.

The return statement

The return statement is used to exit a function and go back to the place from where it was called.

Syntax of return

return [expression_list]

This statement can contain an expression that gets evaluated and the value is returned. If there is no expression in the statement or the return statement itself is not present inside a function, then the function will return the None object.

For example:

>>> print(greet("May"))
Hello, May. Good morning!
None

Here, None is the returned value since greet() directly prints the name and no return statement is used.

Example of return

def absolute_value(num):
    """This function returns the absolute
    value of the entered number"""

    if num >= 0:
        return num
    else:
        return -num


print(absolute_value(2))

print(absolute_value(-4))

Output

2
4

How Function works in Python?

Working of functions in Python

Scope and Lifetime of variables

Scope of a variable is the portion of a program where the variable is recognized. Parameters and variables defined inside a function are not visible from outside the function. Hence, they have a local scope.

The lifetime of a variable is the period throughout which the variable exists in the memory. The lifetime of variables inside a function is as long as the function executes.

They are destroyed once we return from the function. Hence, a function does not remember the value of a variable from its previous calls.

Here is an example to illustrate the scope of a variable inside a function.

def my_func():
	x = 10
	print("Value inside function:",x)

x = 20
my_func()
print("Value outside function:",x)

Output

Value inside function: 10
Value outside function: 20

Here, we can see that the value of x is 20 initially. Even though the function my_func() changed the value of x to 10, it did not affect the value outside the function.

This is because the variable x inside the function is different (local to the function) from the one outside. Although they have the same names, they are two different variables with different scopes.

On the other hand, variables outside of the function are visible from inside. They have a global scope.

We can read these values from inside the function but cannot change (write) them. In order to modify the value of variables outside the function, they must be declared as global variables using the keyword global.

Types of Functions

Basically, we can divide functions into the following two types:

Built-in functions - Functions that are built into Python.
User-defined functions - Functions defined by the users themselves.

What are the 4 types of functions in Python?

Types Of Python Functions Python Built-in Functions. Python Recursion Functions. Python Lambda Functions.

What are the main types of functions in Python?

There are two basic types of functions: built-in functions and user defined functions. The built-in functions are part of the Python language; for instance dir , len , or abs . The user defined functions are functions created with the def keyword.

What are functions in Python?

A function is a block of code which only runs when it is called. You can pass data, known as parameters, into a function. A function can return data as a result.

How many types of functions are available in Python?

Mainly, there are two types of functions: User-defined functions – These functions are defined by the user to perform a specific task. Built-in functions – These functions are pre-defined functions in Python.

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