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Python Chapter-4

This document covers user-defined functions in Python, explaining their purpose, syntax, and types, including built-in functions, positional, keyword, and default parameters. It also introduces lambda functions, recursion, modules, and packages for organizing code. The document emphasizes the reusability of functions and how to define and call them effectively.

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Akshat Joshi
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65 views16 pages

Python Chapter-4

This document covers user-defined functions in Python, explaining their purpose, syntax, and types, including built-in functions, positional, keyword, and default parameters. It also introduces lambda functions, recursion, modules, and packages for organizing code. The document emphasizes the reusability of functions and how to define and call them effectively.

Uploaded by

Akshat Joshi
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Python Programming

PIET CSE Dept.


CHAPTER-4
User Defined Function
What is Function?
➢ Group of statements to perform particular task

➢ Takes arguments as input


➢ Returns the result after manipulation

➢ Two kinds of function


➢ Built – in functions : print(), input()
➢ User defined functions

Image source : Google


Function in Python
➢ Python uses ‘def’ keyword to create user defined function
➢ Define function once and call it many times to reuse
➢ Syntax

❑ Function Definition

def <function_name> (<arguments>) :


# function statement

❑ Function Calling

<function_name>()
Arguments
➢ Input values given to function
➢ Arguments are specified by parameters in function definition

Parameters

Arguments
Return Values
➢ Whatever function gives as outcome is defined as return values
➢ Uses ‘return’ keyword
Return Values
Multiple Parameters
➢ Positional Parameter : Arguments values are identified based on their
position

Argument at pos = 0

Argument at pos = 1
Multiple Parameters

➢ Keyword Parameter : Arguments values are identified based on their


names
Multiple Parameters
➢ Default Parameter : Arguments values can be default

❑ Try calling ‘printinfo(30 , ‘Nita’)’


No need to worry about number of arguments
Accepts
multiple
arguments

You get
tuple of
arguments
Lambda Function
➢ Anonymous functions at runtime
➢ Can take any number of arguments
➢ Can only have one expression
➢ Uses ‘lambda’ keyword to define Arguments

Image source : Google


Recursion : When function call itself
Recursion : When function call itself

Factorial = fact (3)

return (3 * fact(2) ) = 6

return (2 * fact(1) ) = 2

1
Modules
➢ Logically organize your python code in module
➢ Module is just a python file
➢ Module can define functions, classes, variables

daily.py weekly.py
Packages
➢ Hierarchical organization of modules
➢ Package is a directory consists of modules and file named as : __init__.py
weatherman
weatherman is a package
consists of daily and weekly
modules

➢ Use ‘weatherman’ package in another python file using ‘from’ and ‘import’ statement
www.paruluniversity.ac.in

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