Python Functions and Modules Detailed Notes.pptx

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4.Functions and Module

Copyright © 2021, ABES Engineering College
General Guideline
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To describe the importance of functions in Python
Objective of Functions and Modules
To explain the function definition in Python
To develop python programs with functions
To use the void functions and return statements
To explain the difference between different function argument types and use them
To select built-in functions in Python to write programs in Python.

4
Topics Covered
Day 1
4.1 Introduction to
Functions
• 4.1.1 Arguments and
parameters
• 4.1.2 Return
statement
Day 2
4.1 Introduction to
Functions
• 4.1.3 Types of
Function arguments
• 4.1.4 Scope and
Lifetime of variables
Day 3
4.2 Anonymous and
Higher Order Function
• 4.2.1 Anonymous
Function
Day 4
4.2 Anonymous and
Higher Order Function
• 4.2.2 First Class
Function and Higher
Order Function

5
Topics Covered
Day 5
4.3 Modules
• 4.3.1 Creation of
module
• 4.3.2 Importing
module
• 4.3.3 Standard Built-In
Module
Day 6
4.4 Iterative Built-in
Functions

6
4.1 Introduction to functions
4.1.1 Argument and parameters
4.1.2 Return statement
4.1.3 Types of function arguments
4.1.4 Scope and lifetime of variables.
Session Plan - Day 1

7
Introduction
A large program is divided into small blocks of code called functions, to:
 Increase the reusability of code.
 Ease of programming.
Function is a group of all statement(activities) that perform a specific
task.

8
Syntax
The syntax of function definition is:

 Avoid duplication of the similar type of codes
 Increases Program readability and Improved Concept Clarity
 Divide the bigger problem into smaller chunks
 Reusability of code
9
Benefits of Using Functions:

In real world scenario, we need to group all the activities related to a specific
task, like:
1. A task of maintaining student’s basic details involves a group of different activities like:
Collecting their name, branch, batch, age, aadhar number, etc.
2. Similarly, the task of maintaining marks of students involves a group of different activities
like: Collecting marks of English, Physics, Chemistry, Mathematics, etc.
10
Example

 We can create three functions like:
 basic_details ()
 marks()
 work()
11
Contd..

Contd..
12
Function 1: basic_details ()

Contd..
13
Function 2: marks ()

Contd..
14
Function 3: work ()

A function is called using function name through calling environment.
The syntax of function call is:
15
Function Call

16
Flow chart

17
Argumentsand parameters
 Arguments are used to pass the information to the functions.
 They are mentioned after function name inside the parentheses in function
calling statement.
 Any number of arguments can be added by separating them by commas.
Note: The number of parameters in function definition must be same as the number
of arguments in function calling statement.

Write a python program to determine the greater number among two numbers
using function greater(a), by passing one number as argument in function
calling.
18
Example 1

19
Example 2
Write a python program to determine the greater number among two numbers by
passing both the number as argument in function calling.

 Return statement indicate the end of function execution.
 It is also used to return the values or results to the function calling
statement.
20
Return statement

Write a python program to demonstrate the return statement of function for the
addition of two numbers.
21
Example 1

1. Which keyword is used for function?
a) Fun
b) Define
c) Def
d) Function
22
Review Questions

2. What will be the output of the following Python code?
a) 432
b) 24000
c) 430
d) No output
23

24
4.1 Introduction to functions
 4.1.3 Types of Function arguments
 4.1.4 Scope and Lifetime of variables

There are five types of arguments in Python function:
25
Types of Function arguments

Default arguments are values that are provided in the function definition.
Syntax:
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Defaultarguments :
Note: Function can have any number of default arguments. If the values are provided
to the default arguments during the function calling, it overrides the default value.

Write a python program to greet a person with person name and message
provided in function calling statement. If message not provided in function call,
then print a default message “Hi !!”.
27
Example1

Default arguments are keyword arguments whose values are assigned at the
time of function definition.
Syntax:
28
Keywordarguments :

Write a program to demonstrate keyword arguments.
29
Example1

Positional arguments are arguments that need to be included in the proper
position or order while calling the function.
Syntax:
30
Positionalarguments :

Write a program to demonstrate positional arguments.
31
Example1

 When we are not sure in the advance that how many arguments our function
would require.
 This kind of situation is handled through function calls with an arbitrary
number of arguments.
32
ArbitraryArguments
Note: We define the arbitrary arguments while defining a function using the
asterisk (*).

There are two types of arbitrary arguments as illustrated in the given figure
below.
33
Types of ArbitraryArguments

The special syntax *args in function definitions is used to pass the
variable number of arguments to a function.
34
*args
Note: Generally, * args is used by convention but you can take any variable
for example *abc will work in same way as * args.

Write a program to demonstrate *args arbitrary arguments.
35
Example 1

The **kwargs function in python is used to pass an arbitrary number of keyword
arguments called kwargs.
Note: ** (Double star allows us to pass variable number of keyword
arguments). This turns the identifier-keyword pairs into a dictionary within the
function body.
36
**kwargs

Write a program to demonstrate **kwargs arbitrary arguments.
37
**kwargs

Write a program using this function to generate perfect numbers from 1 to 1000. [An
integer number is said to be “perfect number” if its factors, including 1(but not the
number itself), sum to the number. E.g., 6 is a perfect number because 6=1+2+3].
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**kwargs

 Let’s consider a situation that you book a train ticket in sleeper coach and
you got berth in S1 coach and 48 seat number.
 Now your ticket is valid for mentioned train and coach only this is called
scope of your ticket.
 Your ticket would expire after mentioned journey date and that is called
lifetime.
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ScopeandLifetimeofvariables

 Scope: The scope of a variable determines its accessibility and availability
in different portions of a program. Their availability depends on where they
are defined.
 Lifetime: The lifetime of a variable is the time during which the variable
stays in memory.
40
ScopeandLifetimeofvariables

Three kinds of variables in Python:
 Global Variable
 Local Variables
 Non local variables
41
Types of variables

42
Demonstration of Local and Global

Variables that are declared outside of a function are known as global variables.
Example: Write a program to create global variable in python.
43
Global Variables

 These are variables which are defined inside a function.
 Their scope is only to that function.
 They cannot be accessed from the outside of the function.
Example: Write a program to create local variable in python.
44
Local Variables

45
Example: Local and global variable in one program.

46
Example: To modify the variable outside of the current
scope.

 Nonlocal variables are used in nested functions.
 When a variable is either in local or global scope, it is called a nonlocal
variable.
47
Non - Local Variables
Note: Nonlocal keyword will prevent the variable from trying to bind locally
first, and force it to go a level 'higher up'.

 Nonlocal variables are used in nested functions.
 When a variable is either in local or global scope, it is called a nonlocal
variable.
48
Non - Local Variables
Note: Nonlocal keyword will prevent the variable from trying to bind
locally first, and force it to go a level 'higher up'.

49
Example 1
A program to create local variables for nested functions.

50
Example 2
A program to use nonlocal keyword for nested functions.

What will be the output of the following Python code?
a) 9
b) 3
c) 27
d) 30
51
Review Questions

a) 9
27
b) 27
9
c) None of the above
d) Both of the above
52

53
4.2 Anonymous and Higher Order Function
4.2.1 Anonymous Function
4.2.1 Lambda Function

54
Anonymous Function
 Sometimes we only have single expression to evaluate, so rather than
creating regular function we create anonymous Function.
 These functions do not have return statement, because by default evaluated
single expression is returned.
 This is one liner code and have following properties –
 Function without name
 One expression statement but any number of arguments.

55
Syntax

56
Scenario 1
Suppose we want to increment the value of variable by five, without writing
lengthy code we can use lambda function.

57
Example 1
A program to add three values, using multiple arguments in lambda function.

58
Example 2
A program using lambda function to calculate the simple interest.

1. Python supports the creation of anonymous functions at runtime,
using a construct called __________
a) lambda
b) pi
c) anonymous
d) none of the mentioned
59
Review Questions

2. What will be the output of the following Python code?
a) 48
b) 14
c) 64
d) None of the mentioned
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61
4.2 Anonymous and Higher Order Function
 4.2.2 First Class Function and
 4.2.2 Higher Order Function

62
First Class Function and Higher Order Function
 In first class function, function which can be passed as an argument.
 Functions which take first class function as an argument are called Higher
order function.
Syntax:

63
Properties of First-Class Function:
 Function can be passed as an argument into another function.
 Function can be assigned to a variable.
 Function can be returned from other function.

64
Properties of High Order Function:
 Function can take other function as an argument.
 Function can return other function.

 def loud(name):
 return name.upper()
 def soft(name):
 return name.lower()
 def speak(fun):
 print("hello word")
 return fun("xyz")
 print(speak(soft))
Speak is high order function and loud and soft is first
class function
65

 def apply_operation(func, x, y):
 return func(x, y)

def multiply(a, b):
 return a * b

print(apply_operation(multiply, 3, 4))
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 Built-in higher order functions are capable of taking other function as
argument.
 These higher order functions are applied over a sequence of data.

67
Built-in Higher order function in Python

First higher order function we would discuss is map function.
Syntax:
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Map ()

 nums = [1, 2, 3]
 squares = list(map(lambda x: x ** 2, nums))
 print(squares) # Output: [1, 4, 9]
 Map is high order function
 And lambda is first class function
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One important thing to note that map function always returns map object.
Syntax:
70
Contd..

To access values, we need to type cast map object as some sequence
datatype like lists, tuple, etc.
71
Contd..

A program to convert a string of upper-case words into lower case.
72
Contd..

Filter function is the high order function which takes a filtering criterion, need
to apply on any sequence.
For example, in a bucket of balls of different colors, we have to find only
black color balls, then filter function would work.
Syntax:
73
Filter()

 balls = ["red", "blue", "black", "green", "black", "yellow"]
 black_balls = list(filter(lambda color: color == "black", balls))
 print(black_balls)
74

A list of integers find out even numbers.
75
Contd..

Reduce is used in such scenarios where the values in the iterable would be
calculated to a final value.
For example, take a collection of values (3,4,5) and we need to apply sum to
it. Then we would get 12.
Syntax:
76
Reduce()

 from functools import reduce
 numbers = [1, 2, 3, 4, 5]
 # Use reduce to sum the list
 total = reduce(lambda x, y: x + y, numbers)
 print(total)
77

A program to sum numbers of a list using reduce function.
78
Example 1

 Create a function that takes another function and applies it to a name.
 From a list of fruits, filter out those that start with the letter "a".
 Double each numbers in the list using map
 Calculate the product of all elements in the list using reduce()
 A company wants to increase the salaries of employees by 10%. You are
given a list of current salaries.
 salaries = [40000, 50000, 60000, 70000]
79

Practice Hackerrank Question
 https://www.hackerrank.com/challenges/the-minion-game/problem?
isFullScreen=true
80

a) 2
b) 4
c) error
81
Review Questions

a) 2
b) 1
c) error
82

83
4.3 Modules
• 4.3.1 Creation of module
• 4.3.2 Importing module
• 4.3.3 Standard Built-In Module

84
Introduction
As length of program grows in size and to maintain the reusability of some code we start writing
function. Now if you want to use same function/functions in another program instead of writing
their definition then module comes into picture.
Python provides us to create our own module or provides use to use rich source of given
module to increase the reusability.
Python module can be imported into any program
In python module is simply a python file containing python code, it may contain
statements, functions, methods and classes.

85
Creation of module
A file containing Python code, for example: calc.py, is called a module, and its name would be
calc. A module is created simply putting all functions/statements in one python file

86
Contd..
A file containing Python code, for example: calc.py, is called a module, and its name would be
calc. A module is created simply putting all functions/statements in one python file
Code illustrates that how
to create a module name
‘calc’, which contains the
user defined functions of
addition, subtraction,
multiplication and division
and area.

87
Importing module
To use the module in any application or program we need to import that module using import
keyword.
We can import module in multiple
ways –
• import module-name
• import ... as ...
• from ... import ...

88
Contd..
When we use “import module-name” syntax, it will import all functions/statements from that
module and function will call using module-name and dot operator.

89
Contd..
import ... as ...
We use import ... as ... to give a module name a short alias name while importing it.

90
Contd..
import ... as ...
Example: We import module calc using alias name ‘m’. It will import all functions / statements from
that module and function will call using alias name and dot operator.

91
Contd..
from ... import ...
The from…. Import … statement allows us to import specific functions/variables from a module
instead of importing everything.

92
Contd..
from ... import ...
Multiple function can also be imported using comma (,) operator.
from calc import addition, subtraction
We can also use ‘*’ , for importing all function/statements.
from calc import *

93
Standard Built-In Module
Python has large number of built in functions similarly python contains some of the pre-defined
modules such as:
math random datetime sys os

94
Contd..
The math Module
Python has set of built-in math functions and also has an extensive math module that allows us to
perform mathematical tasks on data. These include trigonometric functions, representation
functions, logarithmic functions, sine functions, cosine functions, exponential, pi etc.
math.sqrt()
This function will calculate the square root of number.

95
Contd..
math.ceil()
Rounds a number up to the nearest
integer.
math.exp()
Return 'E' raised to the power of
different numbers

96
Contd..
math. factorial()
Return the factorial of a number
math.gcd()
Return the greatest common divisor
of two integers.
math.pow()
Returns the value of x to the power of y.

97
Contd..
math.fsum()
Returns the sum of all items in an
iterable.
math.sin()
Return the cosine of x (measured in
radians).
Refrence : https://docs.python.org/3/library/math.html

98
Contd..
The random Module
This module implements pseudo-random number generators for various distributions. We can
generate random numbers in Python by using random module.
random.seed()
The random number generator needs a number to start with (a seed value).
Use the seed() method to customize the start number of the random number generator.

99
Contd..
random.random()
Return random number between 0.0 and 1.0
random.randint(a,b)
Return random integer between a and b,
including both end points.
random.choice()
Choose a random element from a non- empty
sequence like string, list, tuple etc.
random.shuffle()
The shuffle() method takes a sequence and
reorganize the order of the items.
import random
fruits = ['apple', 'banana', 'cherry',
'mango', 'grape']
random_fruit = random.choice(fruits)
print("Randomly selected fruit:",

100
Contd..
The datetime Module
In python there is no date and time data type so python date time module is used for displaying
dates and times, modifying dates and time in different format.
This module supplies classes to work with date and time. These classes provide a number
of functions and built in methods to deal with dates, times and time intervals.
Note:
Classes and Objects we are going to discuss in Object Oriented Programming in Python.

101
Contd..
The datetime Module
Commonly used classes and associated methods in the datetime m

102
Contd..
The date class
A date object of date class represents a date in year, month and day.

103
Contd..
All method and attributes of date object will be called using ‘d’ object and dot operator.

104
Contd..
The time class
Time object represents local time, independent of any day.

105
Contd..
Create a time object and display hour, minute, second and microsecond in time object.

106
Contd..
The datetime class
Information on both date and time is contained in this class.

107
Contd..
Create a time object and display hour, minute, second and microsecond in time object.
Create a datetime
object and display
year, month, hour,
minute in time
object.
Write a program
to fetch the
current datetime
of system and
print it

108
Contd..
The sys Module
The sys module provides system specific parameters and functions. It gives us information
about constants, functions, and methods of the interpreter.
Following are some important use of sys module:
• Exiting current flow of execution in Python
• Command-line Arguments
• Getting version information of Interpreter
• Set or get recursion depth
For more function visit - https://docs.python.org/3/library/sys.html)

109
Contd..
sys.version
Gives version information of Interpreter.

110
Contd..
sys.argv
It returns a list of command line arguments passed to a Python script.

111
Contd..
sys.argv
Write a python script which print sum of given two value through command line

112
Contd..
sys.argv
Write a python script which print sum of given two value through command line

113
Contd..
sys.getrecursionlimit() and sys.setrecursionlimit()
sys.getrecursionlimit()
method is used to find
the current recursion
limit of the interpreter.
sys.setrecursionlimit()
method is used to set
the recursion limit of the
interpreter

114
Review Questions
 What is the output of the code shown below if the system date is
18th August, 2016?
tday=datetime.date.today()
print(tday.month())
A. August
B. Aug
C. 08
D. 8

115
Review Questions
What is returned by math.ceil(3.4)?
a) 3
b) 4
c) 4.0
d) 3.0
What is returned by math.ceil(3.4)?
a) 3
b) 4
c) 4.0
d) 3.0

116
Review Questions
 What will be the output of the following Python code?
import time
print(time.strftime("%d-%m-%Y"))
a) Print today’s date in string format dd-mm-yy
b) Print today’s date in string format dd-mm-yyyy
c) Error
d) None
 State whether true or false.
t1 = time.time()
t2 = time.time()
t1 == t2
a)True
b)False

117
4.3 Modules
 4.4 Iterative Built-in Functions
Enumerate
Zip
Sorted
Zip

118
Enumerate: This is built-in function provided by Python. This function
assigns count values to the iterable
Iterative Built-in Functions
What is iterable?
Iterable in python is a collection of
items, sequences like lists, tuple or
any object which have multiple
values on which a repeat operation
can be performed, like
name = [‘amit’, ‘ankur’, ‘aditya’, ‘anshul’,
‘anmol’],
here the name has five items in it.

119
When using the iterators, we need to keep track of the number of items in the
iterator. This is achieved by built in method called enumerate.
This enumerated object can directly be used for loops or converted into a list of
tuples using list () method.
Note: by default enumerate starts from 0 but we can change this start value as per our
convenience.
Contd..

120
Contd..
Example : Demonstrating the enumerate usage in printing days of week.

121
Contd..
Enumerate with for loop
Example
Syntax

122
Contd..
Zip
The function returns a zip object, which is an iterator of tuples where the first item in each
passed iterator is paired together, and then the second item in each passed iterator are paired
together etc.
Example
Syntax

123
Contd..
Sorted
.
Python contains a special built in method for sorting the data in a collection. It preserves the
order of previous sequence or collection
Syntax

124
Contd..
Sorted Example

125
Contd..
Reversed
Reversed () function returns the iterator in a reverse order. Iterator can be any sequence such
as list, tuple etc.
Example
Syntax

126
Review Questions
 Which of the following functions can help us to find the version of python that
we are currently working on?
a) sys.version
b) sys.version()
c) sys.version(0)
d) sys.version(1)
 Suppose there is a list such that: l=[2,3,4]. If we want to print this list in
reverse order, which of the following methods should be used?
a) reverse(l)
b) list(reverse[(l)])
c) reversed(l)
d) list(reversed(l))

127
Review Questions
 Which of the following functions is not defined under the sys module?
a) sys.platform
b) sys.path
c) sys.readline
d) sys.argv
 To obtain a list of all the functions defined under sys module, which of the
following functions can be used?
a) print(sys)
b) print(dir.sys)
c) print(dir[sys])
d) print(dir(sys))

128
 In this unit you learnt the importance of using functions and how to use
functions.
 Further you learnt how to define functions, to write functions with
different argument types.
 Further you learnt describe the difference between the in- built functions and user
defined functions,
 Further you to write user defined functions, to use Functions in- built functions,
import math module in to a Python program and to use lambda functions.
Summary

129
1. https://docs.python.org/3/tutorial/controlflow.html
2. Think Python: An Introduction to Software Design, Book by Allen B. Downey
3. Head First Python, 2nd Edition, by Paul Barry
4. Python Basics: A Practical Introduction to Python, by David Amos, Dan Bader, Joanna Jablonski,
Fletcher Heisler
5. https://www.fullstackpython.com/turbogears.html
6. https://www.cubicweb.org
7. https://pypi.org/project/Pylons/
8. https://www.upgrad.com/blog/python-applications-in-real-world/
9. https://www.codementor.io/@edwardbailey/coding-vs-programming-what-s-the-difference-yr0aeug9o
References

130
Thank You

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