[FUNCTION]

[FUNCTION]

Definition: A function is a reusable block of code designed to perform a specific task. Functions help break down complex programs into smaller, manageable parts, improving readability and efficiency.

OR

In Python, a function is a block of reusable code that performs a specific task. You define a function once, and then you can call (use) it anywhere in your code.

OR

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. 

Advantages of Using functions:

• Code Reusability: We can write a function once and reuse it multiple times without rewriting the same code and We can call a function wherever you need it, without rewriting the same logic.
• Modularity: Functions break a large program into smaller, manageable pieces (modules), making it easier to understand and work with
• Improved Readability: Functions with descriptive names make code easier to read and understand
• Easy Debugging and Maintenance: If there's a bug in your program, it's easier to isolate and fix when the logic is encapsulated in functions
• Abstraction: We don’t need to understand the internal workings of a function to use it—just know what input it expects and what output it returns.
• Support for Recursion: Functions can call themselves, which is useful for solving problems like tree traversal or factorial calculation
• Increases program readability: The length of the source program can be reduced by using/calling functions at appropriate places so program become more readable.

Types of Functions:

There are three types of functions in python:

• Built-in Functions:
• Built-in Library Functions
• User-defined Functions
• Lambda Functions (Anonymous Functions)
• Recursive Functions

Built In Functions: These functions are already built in the python library.

• These are pre-defined functions and are always available for use
• In order to use these functions , there is no need to import any module
• We can directly use it , in our program.

                            Example: len()   ,  print()   ,  int()   , input()   , type()  , id() ,ord()

Built-in Library Functions: These functions defined in particular modules. When we want to use these functions in program, we have to import the corresponding module of that function.

• These functions are pre-defined in particular modules
• These can only be used when the corresponding module is imported (like math.sqrt() from the math module or random.randint() from random)

                               Example:  math module: sin()     cos()     sqrt()    fabs()    ceil()   floor()

Sr	Function	Description	Example	Output
1	sqrt( )	Returns the square root of a number	>>>math.sqrt(49)	7.0
2	ceil( )	Returns the upper integer	>>>math.ceil(81.3)	82
3	floor( )	Returns the lower integer	>>>math.floor(81.3)	81
4	pow( )	Calculate the power of a number	>>>math.pow(2,3)	8.0
5	fabs( )	Returns the absolute value of a number	>>>math.fabs(-5.6)	5.6
6	exp( )	Returns the e raised to the power i.e. e3	>>>math.exp(3)	20.085536923187668

                        >>> sqrt(144)                   NameError: name ‘sqrt’ is not defined

                        >>> import math

>>> math.sqrt(144)

           12.0

Example:

import calendar year = 2024 print(calendar.calendar(year))

import calendar year = 2024 month = 4 print(calendar.month(year,month))

random module: random()    uniform()   randrange()    choice()  randint()    shuffle()

       randint( ) function generates the random integer values including start and end values.

Syntax:  randint(start, end)

   ØIt has two parameters. Both parameters must have integer values.

Example:

import random

n=random.randint(3,7)

                                              *The value of n will be 3 to 7.