Problem Solving and Python Programming

KARPAGAM INSTITUTE OF TECHNOLOGY,
COIMBATORE - 105
Course Code with Name : GE8151 - Problem Solving and Python Programming
Staff Name / Designation : A.Mahalakshmi / Assistant Professor
Department : Information Technology
Year / Semester : I / I
Department of Information Technology

UNIT I - ALGORITHMIC PROBLEM SOLVING
SYLLABUS:
Algorithms, building blocks of algorithms (statements, state,
control flow, functions), notation(pseudo code, flow chart,
programming language), algorithmic problem solving,
simple strategies for developing algorithms (iteration,
recursion).
Illustrative problems: find minimum in a list, insert a card in
a list of sorted cards, guess an integer number in a range,
Towers of Hanoi.
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ALGORITHMS
• Step-by-step procedure to solve a problem.
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Karpagam Institute of Technology

CHARACTERISTICS OF AN ALGORITHM
• The instructions should be in a ordered manner.
• The instructions must be simple and concise.
• They must not be ambiguous.
• The algorithm must completely and definitely
solve the problem.
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ADVANTAGES OF ALGORITHM
 Easy to understand.
 Programs can be easily developed.
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Write the algorithm to find the sum and average of
given 2 numbers.
Step1 : Start
Step2 : Read values of A and B
Step3 : Calculate SUM =A+B
Step4 : Calculate AVERAGE = (SUM/2)
Step5 : Print Values of SUM and AVERAGE
Step6 : Stop
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BUILDING BLOCKS OF ALGORITHMS
Statement
State
Control Flow
Functions
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STATEMENT
• Statement is a single action in a computer.
• In a computer statements might include some of
the following actions,
Input data-information given to the program
Process data-perform operation on a given input
Output data-processed result
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STATE
• Transition from one process to another process
under specified condition within a time is
called state.
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CONTROL FLOW
• The process of executing the individual
statements in a given order is called control
flow.
• The control can be executed in three ways
 Sequence
 Selection
 Iteration
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SEQUENCE
• All the instructions are executed one after another
is called sequence execution.
• Example: Sum of two numbers:
Step 1: Start
Step 2: Read the values of a and b
Step 3: calculate c=a+b
Step 4: Display c
Step 5: Stop
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SELECTION
• Selection execution is based upon the condition.
• If the conditional test is true, one part of the
program will be executed.
• Otherwise, it will execute the other part of the
program.
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Write an algorithm to check whether he is
eligible to vote?
Step 1: Start
Step 2: Get age
Step 3: if age >= 18 print “Eligible to vote”
Step 4: else print “Not eligible to vote”
Step 6: Stop
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ITERATION
• Set of statements are executed again and again based upon
conditional test.
• Write an algorithm to print all ‘n’ natural numbers
Step 1: Start
Step 2: get n value.
Step 3: initialize i=1
Step 4: if (i<=n) go to step 5 else go to step 7
Step 5: Print i value and increment i value by 1
Step 6: go to step 4
Step 7: Stop
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FUNCTIONS
• Function is a sub program which consists of block of code(set of
instructions) that performs a particular task.
• Algorithm for addition of two numbers using function
Main function
Step 1: Start
Step 2: Call the function add( )
Step 3: Stop
Sub function
Step 1: Function start
Step 2: Get a, b Values
Step 3: add c=a+b
Step 4: Print c
Step 5: Return
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FLOW CHART
• Pictorial representation of an algorithm.
• Since it is a visual representation, it helps to understand the logic of
the program.
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Draw a flowchart to find the sum and average
of given two numbers.
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Draw a flowchart to find the smallest of given
two numbers.
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PSEUDOCODE
• Pseudo code only describes the logic to develop a program
and it can be translated to any computer language code.
• Keywords should be highlighted by capitalizing them.
• Using Keywords:
 Input : READ, OBTAIN, GET
 Output : PRINT, DISPLAY, SHOW
 Compute : COMPUTE, CALCULATE, DETERMINE
 Initialize : SET, INITIALIZE
 Add one : INCREMENT, BUMP
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Write a pseudo code to accept two numbers from the
keyboard and calculate the sum and
product of them, also display the result on the
monitor screen.
BEGIN
READ A, B
CALCUALTE Sum=A+B
DISPLAY Sum
END
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PROGRAMMING LANGUAGE
• Computer programming languages are used to communicate
instructions to a computer.
 Interpreted Programming Languages
 Functional Programming Languages
 Compiled Programming Languages
 Procedural Programming Languages
 Scripting Programming Languages
 Markup Programming Languages
 Logic-Based Programming Languages
 Concurrent Programming Languages
 Object-Oriented Programming Languages
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PROGRAMMING LANGUAGE CONTD..
Interpreted Programming Languages
• An interpreted language execute instructions
directly, without previously compiling a
program into machine-language instructions.
• Examples: APL, BASIC, ICI, J, Lisp, Lua, M,
Pascal, Perl, Python, Ruby, S-Lang, spin
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Functional Programming Language:
• They focus on the application of functions.
• Many functional programming languages are bound
to mathematical calculations.
Examples:-
• ML, Joy, Kite, Clean, OPAL, Q
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Compiled Programming Languages
• A compiled language is a programming
language whose implementations are typically
compilers.
• Examples: Ada, ALGOL, C, C++, C#,
COBOL, etc.
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Procedural Programming Languages
• Procedural (imperative) programming implies
specifying the steps that the programs should
take to reach to an intended state.
• Examples: Bliss, ChucK, CLIST, HyperTalk,
Modula-2, Oberon, Component, Pascal,
MATLAB, PL/C, PL/I, Rapira, RPG
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Scripting Languages
• Scripting languages are programming
languages that control an application.
• Examples: AppleScript, BeanShell,
ColdFusion, F-Script, JASS, PHP, VBScript,
Windows PowerShell
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Markup Languages
• A markup language is an artificial language
that uses annotations to text that define how
the text is to be displayed.
• Examples: Curl, SGML, HTML, XML,
XHTML
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Logic-based Programming Languages
• Logic programming is a type of programming
paradigm which is largely based on formal
logic.
• Examples: ALF, Fril, Janus, Oz, Poplog,
Prolog, ROOP
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Concurrent Programming Languages:
• It is a computer programming technique, which
executes the operation concurrently – either within
single computer or across number of systems.
Examples:
• ABCL, Concurrent Pascal, E, Joule, SALSA, Pict,
SR, etc.
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Object-Oriented Programming Languages
• Object-oriented programming (OOP) is a
programming paradigm based on the concept of
“objects”, which may contain data, in the form of
fields, often known as attributes; and code, in the
form of procedures, often known as methods.
• Examples: IO, Slate, Self, Scala, Prograph,
Oxygene, Moto, MOO, Lava, BETA, Agora
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ALGORITHMIC PROBLEM SOLVING
➢Understanding the problem
➢Ascertain the capabilities of the computational
device
➢Exact /approximate solution
➢Decide on the appropriate data structure
➢Algorithm design techniques
➢Methods of specifying an algorithm
➢Proving an algorithms correctness
➢Analyzing an algorithm
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UNDERSTANDING THE PROBLEM
• The problem given should be clearly and
completely understood.
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DETERMINING THE CAPABILITIES OF
THE COMPUTATIONAL DEVICE
• After understanding the problem, speed and
memory availability of the device are to be
noted.
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EXACT /APPROXIMATE SOLUTION
• Once algorithm is devised, it is necessary to show that
how it computes answer for all the possible legal
inputs.
• Examples of Exact solution problems are
i) Computing addition of 2 numbers.
ii) Find the given number is prime or not.
Examples of Approximate solution problems where an
exact solution cannot be obtained are
i) Finding a square root of number.
ii) Solutions of non linear equations.
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DECIDE ON THE APPROPRIATE DATA
STRUCTURE
• Data type is a well defined collection of data with the well
defined set of operations on it.
• A data structure is basically a group of data elements.
• The Elementary data structures are as follows,
 List: Allows fast access of data
 Sets: Treat data as element of a set. Allows application of
operations such as intersection, Union and equivalence.
 Dictionaries: Allows data to be stored as a key value pair.
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ALGORITHM DESIGN TECHNIQUES
• Creating an algorithm is an art.
• By mastering these design strategies, it will
become easier to devise new and useful
algorithms.
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METHODS OF SPECIFYING AN
ALGORITHM
• Use of natural language or pseudocode.
• Flow Chart
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PROVING AN ALGORITHMS
CORRECTNESS
• It is necessary to prove that algorithm
computes solutions for all the possible valid
input.
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ANALYZING THE PERFORMANCE OF
ALGORITHMS
• An algorithm is analyzed to measure its
performance in terms of CPU time and memory
space required to execute that algorithm.
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SIMPLE STRATEGIES FOR DEVELOPING
ALGORITHMS (ITERATION,
RECURSION)
ITERATION
• A Loop is one or more instructions that the computer
performs repeatedly.
• Algorithm: Write the algorithm to print “1 to 5”
Step1 : Start
Step2 : Initialize the value of i as 1
Step3 : Print i and increment the value of i
Step 4: Repeat the Step 3 until the value of i <=5.
Step 5 : Stop
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RECURSION
• A function that calls itself is known as recursive function and the
phenomenon is called as recursion.
• Algorithm: Write an algorithm to find the factorial of a given
number
Main Program:
Step 1: Start
Step 2: Read n
Step 3: Call the sub program as f=fact(n)
Step 4 : print f value
Step 5: Stop
Sub Program:
Step 1: If n==0 or n==1 return 1 to the main program otherwise go to
step 2
Step 2: return n*fact(n-1) to main program
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FINDING MINIMUM IN A LIST
Step 1:Start
Step 2: Read the list of numbers as L
Step 3: Set Min to list[0]
Step 4: For each number x in the list L, compare it
to min
Step 4a: If x is smaller, then assign min to x
Step 5: Print min
Step 6: Stop
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GUESS AN INTEGER NUMBER IN A
RANGE
Step 1: Start
Step 2: Generate a random number in between 1 and 100
Step 3: Get the guessed number from the user
Step 4:If the random number is equal to the guessed number
print guessing is correct.
Step 5: Otherwise If the random number is greater than the
guessed number print guessing is too high and go to
step 7
Step 6: Otherwise print guessing is too high and go to step 7.
Step 7: Stop
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INSERT A CARD IN A LIST OF SORTED
CARDS
Step 1 - Start
Step 2 - Read the list of sorted cards.
Step 3 - If it is the first card, it is already sorted. return 1;
Step 4 - Pick next card
Step 5 - Compare with all cards in the sorted sub-list
Step 6- Shift all the cards in the sorted sub-list that is
greater than the value of the card to be inserted.
Step 5 - Insert the card
Step 6 - Repeat until list is sorted.
Step 7 - Stop
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TOWERS OF HANOI
• Problem:
• Tower of Hanoi is a mathematical puzzle with
three rods and ‘n’ number of disks.
• These disks are in different sizes and stacked
upon in an ascending order, i.e the smaller one
sits over the larger one.
• The objective is to move all the disks to some
another tower without violating the sequence
of arrangement.
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RULES TO BE FOLLOWED
• Only one disk can be moved among the towers
at any given time.
• Only the “top” disk can be removed.
• No large disk can sit over a small disk.
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VIDEO TUTORIAL
S.NO TOPIC LINK
1 Minimum in a list https://youtu.be/5Y1rxCMY_jU
2 Insert a Card in a list of
Sorted Cards
https://youtu.be/Mow8rdOKrbY
3 Guess an integer number
in a range
https://youtu.be/pmDKRJdqT1E
4 Tower of Hanoni https://youtu.be/hKUwLe7bpwo
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SUMMARY OF UNIT I
• Algorithm, Flow chart, Pseudo code
• Building Blocks of an Algorithm
• Algorithmic Problem Solving Technique
• Simple Strategies for developing an algorithm
• Illustrative Problems for developing an algorithms
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ASSIGNMENT QUESTIONS
S.NO QUESTIONS BLOOMS LEVEL
1 Apply the rules of an algorithm and
pseudocode to find whether the given
number is positive, negative and zero.
K3
2 Apply the rules of an algorithm and
pseudocode to find the factorial of a given
number using recursion.
K3
3 Write a pseudo code for converting celsius
of a given value into fahrenheit.
K3
4 Develop a flow chart for performing
Towers of Hanoi operation.
K5
5 Design a flow chart for calculating simple
interest
K5
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QUIZ-TEST YOUR KNOWLEDGE
• https://docs.google.com/forms/d/e/1FAIpQLSe
crZ0M-AnDkGI5HOSpzjHrHiDacakocv_-u2K
s_zul55YF0w/viewform
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UNIT II DATA, EXPRESSIONS, STATEMENTS
SYLLABUS:
Python interpreter and interactive mode; values and types: int,
float, boolean, string, and list; variables, expressions, statements,
Tuple assignment, precedence of operators, comments; modules
and functions, function definition and use, flow of execution,
parameters and arguments;
Illustrative programs: exchange the values of two variables,
circulate the values of n variables, distance between two points.
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PYTHON INTERPRETER AND INTERACTIVE MODE
INTERACTIVE MODE PROGRAMMING:
• Interactive mode is a command line shell which gives
immediate feedback for each statement.
• In this mode, the prompts for the next command usually have
three greater-than signs (>>>).
• Example- A sample interactive session:
>>> 5
5
>>> print(5*7)
35
>>> "hello" * 4
'hellohellohellohello'
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PYTHON INTERPRETER AND INTERACTIVE MODE
CONTD..
SCRIPT/INTERPRETER MODE PROGRAMMING
• In script mode, execution of the script begins and continues
until the script is finished.
• Example:
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VALUES AND TYPES
• VALUE – refers to the basic things in a program works which
can be like a letter or a number.
• TYPE - refers to the data type, which is used to find the type
of data.
Following are the various basic types of a value:
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S.NO TYPES EXAMPLE OF VALUES
1 Int 10,100,-256,789656
2 Float 3.14,2.56789,-21.9
3 Boolean True or False
4 String “Hai” or ‘Hi’
5 List [0,1,2,3,4]
6 Tuple (0,1,2,3,4)
7 Dictionaries {1: “Hai”, 2: “Welcome”}

VALUES AND TYPES CONTD..
• INTEGER- it is represented by a whole number.
>>>type(3)
<type ‘int’>
• FLOAT-Numbers with a decimal point
>>>type(3.2)
<type 'float'>
• BOOLEAN-it is represented by TRUE or FALSE
>>> bool(1)
True
>>> bool(0)
False
>>>type(2>3)
<class ‘bool’>
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VALUES AND TYPES CONTD..
• STRING - values with quotes like single, double, triple
>>>type('17')
<type 'str'>
• LIST- collection of elements in square bracket [ ]
>>>a=[1,2,3]
>>>type(a)
<tupe ‘list’>
• TUPLE - collection of elements in paranthesis ( )
>>>a=(1,2,3)
>>>type(a)
<type ‘tuple’>
• DICTIONARY – Collection of elements in curly braces { } with key:value
pair
>>>a={1: “hai”, 2: “welcome”}
>>>type(a)
<type ‘dict’>
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VARIABLES
• Variables are defined as reserved memory locations to store
values.
Rules for Naming Variables
• Variable names can contain letters, symbols like underscore
(__) and numbers.
• They begin with a letter not numbers.
• Both uppercase and lowercase letters are used.
• Keywords cannot be used as variable names.
• Example for valid identifier
• abc, xy12, good_start
• Example for non-valid identifier
• 12xy, x$y
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EXPRESSIONS
• An expression is a combination of values, variables,
and operators.
• Examples:
–17
–x
–x + 17
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STATEMENTS
• Each and every instruction or line in the program is
called as statements.
• Example:
A=10 #assignment statement
B=20 #assignment statement
C=A+B #assignment statement
print(C) #print statement
Output :
30 #output statement
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TUPLE ASSIGNMENT
• Python has a very powerful tuple assignment feature that
allows a tuple of variables on the left of an assignment to be
assigned values from a tuple on the right of the assignment.
• For example, to swap a and b:
a=10
b=20
temp = a
a = b
b = temp
• Tuple assignment solves this problem neatly:
(a,b) = (b,a)
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PRECEDENCE OF OPERATORS
ORDER OF OPERATIONS:
• When more than one operator appears in an expression, the
order of evaluation depends on the rules of precedence.
• The acronym PEMDAS is a useful way to remember the rules:
– Parentheses have the highest precedence
• 2 * (3-1) is 4, and
• (1+1)**(5-2) is 8.
- Exponentiation has the next highest precedence
• 2**1+1 is 3, not 4, and
• 3*1**3 is 3, not 27.
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PRECEDENCE OF OPERATORS CONTD..
• Multiplication and Division have the same precedence, which
is higher than Addition and Subtraction, which also have the
same precedence.
– 2*3-1 is 5, not4, and
– 6+4/2 is 8, not 5.
• Operators with the same precedence are evaluated from left to
right (except exponentiation).
– So in the expression degrees / 2 * pi, the division happens
first and the result is multiplied by pi.
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PRECEDENCE OF OPERATORS CONTD..
Operator Description
** Exponentiation raise to the power
~ ,+,- Complement, unary plus and minus
*, /, %, // Multiply, divide, modulo and floor division
+, - Addition and subtraction
>> , << Right and left bitwise shift
& Bitwise 'AND'
^, | Bitwise exclusive `OR' and regular `OR'
<=, <, >, >= Comparison operators
<>, ==, != Equality operators
=, %=, /=, //=, -=, +=, *=, **= Assignment operators
is, is not Identity operators
in, not in Membership operators
not or and Logical operators
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COMMENTS
• Comment is a piece of program text that the interpreter ignores
but that provides useful documentation to programmers.
• Comments start with the # symbol
Example:
# compute the sum of two numbers
C=A+B
• In this case, the comment appears on a line by itself. We can
also put comments at the end of a line
C=A+B #sum of two numbers
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MODULES AND FUNCTIONS
• Module is a file consisting of Python code.
• A module can define functions, classes and variables.
Example:
a="Dora"
def print_func(a):
print ("Hello : ", a)
return
print_func(a)
Output:
Hello : Dora
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MODULES AND FUNCTIONS CONTD..
• The modules can be imported by the following ways:
 The import statement
 The from...import Statement
 The from...import * Statement
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The import statement
• We can use any Python source file as a module by
executing an import statement in some other Python
source file.
• The import has the following syntax,
import module1, module2, …….moduleN
Example-
import math
print(math.sqrt(4))
Output
2.0
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The from….import statement
• In Python’s from statement, lets us import specific attributes
from a module into the current namespace.
• The from…import statement has the following syntax,
from modname import name1, name2,…nameN
Example-
moduleAccess.py
from sample import a,b
print(a.A())
print(b.B())
Output:
Hai
Hello
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a.py
def A():
print(“Hai”)
b.py
def B():
print(“Hello”)
sample.py

The from….import* statement
• It is also possible to import all names from a module
into the current namespace by using the following
import statement,
from modname import*
• This provides an easy way to import all the items
from a module into the current namespace.
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FUNCTION DEFINITION AND USE
FUNCTION
 Function is a block of code, that are executed when it is called.
 Function blocks begin with the keyword def followed by the
function name and parentheses ( ).
 Any input parameters or arguments should be placed within
these parentheses.
 The code block within every function starts with a colon (:) and
is indented.
 The statement return [expression] exits a function, optionally
passing back an expression to the caller.
 A return statement with no arguments is the same as return
None.
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FUNCTION DEFINITION AND USE CONTD..
Syntax-
def functionname( parameters ):
function_suite
return[expression]
Example-
def printme(str):
print (str)
return
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FUNCTION DEFINITION AND USE CONTD..
USES OF FUNCTION-
It makes the program size smaller.
It involves the concept of modularity.
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FLOW OF EXECUTION
 The order in which statements are executed, which is
called the flow of execution.
 Execution always begins at the first statement of the
program.
 Statements are executed one at a time, in order from
top to bottom.
 During function call, the arguments in the actual
parameters are assigned to the formal parameters.
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FLOW OF EXECUTION CONTD..
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FLOW OF EXECUTION CONTD..
Example-
a=10
b=20
def sum(c,d):
e=c+d
return e
print("Result is :",sum(a,b))
Output:
30
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PARAMETERS AND ARGUMENTS
• Parameters provide the data communication between
calling function and called function.
Two types:
 Actual parameter -This is the argument which is
used in function call.
 Formal parameter - This is the argument which is
used in function definition.
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PARAMETERS AND ARGUMENTS CONTD..
ARGUMENTS - refers to the value.
Types of Arguments
 Required arguments
 Keyword arguments
 Default arguments
 Variable-length arguments
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REQUIRED ARGUMENTS
 Required arguments are the arguments passed to a function
in correct positional order.
Example
def sum(a,b):
c=a+b
return c
print("Result is:", sum(10,20))
Output:
30
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KEYWORD ARGUMENTS
 Here, the caller identifies the arguments by the parameter
name.
Example
def sum(a,b):
c=a+b
return c
print("Result is:", sum(a=10,b=20))
Output:
30
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DEFAULT ARGUMENT:
 Default argument is an argument that assumes a default
value if a value is not provided in the function call for that
argument.
Example
def sum(a=10,b):
c=a+b
return c
print("Result is:", sum(20))
Output:
30
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VARIABLE-LENGTH ARGUMENT
 This is used to process a function with more argument.
Syntax for a function with variable length argument,
def functionname([formal_args,]*var_args_tuple):
function_suite
return[expression]
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Example for Variable-length Argument
def printinfo( arg1,*vartuple):
print ("Output is: ")
print ( arg1)
for var in vartuple:
print (var)
return;
printinfo(10)
printinfo(70,60,50)
Output
10
Output
70
60
50
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EXCHANGE THE VALUE OF TWO VARIABLES
With Temporary Variable
x = input("Enter value of x:")
y = input("Enter value of y:")
temp = x
x = y
y = temp
print('The value of x after swapping:',x)
print('The value of y after swapping:',y)
Output
Enter value of x: 67
Enter value of y: 45
The value of x after swapping: 45
The value of y after swapping: 67
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EXCHANGE THE VALUE OF TWO VARIABLES CONTD..
Without Temporary Variable
x = input("Enter value of x:")
y = input("Enter value of y:")
x= x + y
y = x - y
x = x - y
print('The value of x after swapping:',x)
print('The value of y after swapping:',y)
Output
Enter value of x: 67
Enter value of y: 45
The value of x after swapping: 45
The value of y after swapping: 67
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CIRCULATE THE VALUES OF N NUMBERS
def circulate(A,N):
for i in range of(0,N):
j=len(A)-1
while j>0:
temp=A[j]
A[j]=A[j-1]
A[j-1]=temp
j=j-1
print(‘Circulationt’,A)
return
A=[91,92,93,94,95]
n=int(input(“Enter n:”))
circulate(A,n)
Output
n=2
Circulation 95,91,92,93,94
Circulation 94,95,91,92,93
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DISTANCE BETWEEN TWO POINTS
import math
x1=int(input("Enter the X-Coordinate of first point"))
y1=int(input("Enter the Y-Coordinate of first point"))
x2=int(input("Enter the X-Coordinate of Second point"))
y2=int(input("Enter the Y-Coordinate of Second point"))
distance = math.sqrt( ((x1-x2)**2)+((y1-y2)**2) )
print(distance)
Output
Enter the X-Coordinate of first point 4
Enter the Y-Coordinate of first point 0
Enter the X-Coordinate of Second point 6
Enter the Y-Coordinate of Second point 6
6.324555320336759
2/22/2022 87

VIDEO TUTORIAL
S.No Topic Link
1 Interpreter and Interactive mode https://youtu.be/3lvgY5V8494
2 Operator and it's types with their
Precedence
https://youtu.be/ljaw6cUobtU
3 Circulate the value of n numbers
using slicing operator
https://youtu.be/1Y46EaJAQ4c
4 Distance between two points https://youtu.be/qeZ5kiKJe7c
2/22/2022 88

SUMMARY
 Python Interpreter and Interactive mode
 Values and Data types
 Operators and its Precedence
 Modules and Functions
 Function Parameters and Arguments
 Illustrative Problems
2/22/2022 89

S.No Questions Blooms Level
1 Write a Python programs to check
whether the given number is palindrome
or not
K3
2 Apply the concept of Modules for airlines
system
K3
3 Distinguish between Interpreter mode and
Interactive mode
K4
4 Develop a Python program for finding
Fibonacci sequence of n numbers using
function with recursion
K5
2/22/2022 90

QUIZ - TEST YOUR KNOWLEDGE
• https://forms.gle/uP745eEsYzko6Y2U9
2/22/2022 91

UNIT III CONTROL FLOW, FUNCTIONS
SYLLABUS
Conditionals: Boolean values and operators, conditional (if),
alternative (if-else), chained conditional (if-elif-else);
Iteration: state, while, for, break, continue, pass; Fruitful
functions: return values, parameters, local and global scope,
function composition, recursion; Strings: string slices,
immutability, string functions and methods, string module;
Lists as arrays.
Illustrative programs: square root, gcd, exponentiation, sum
an array of numbers, linear search, binary search.
2/22/2022 92
Karpagam Insitute of Technology
2/22/2022 92

BOOLEAN EXPRESSION
A Boolean expression is a expression that results in either true
or false.
It uses the == operator which compares two operands and
procedures true if both are equal otherwise false.
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CONTROL FLOW
• It is a statement that determines the control flow of a set of
instructions., (ie) it decides the sequence in which the
instructions in a program are to be executed.
• It can either comprise of one or more instructions. Three
fundamental control statements are
 Sequential
 Selection
 Iterative control
94
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TYPES OF DECISION CONTROL STATEMENTS
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SELECTION OR CONDITIONAL BRANCHING
STATEMENT
• The decision control statements usually jumps from one part of
the code to another depending on whether a particular
condition is satisfied or not.
• Python selection statements are:
 If statement
 If-else statement
 If-elif-else statement
 Nested-if statement
96
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ITERATIVE STATEMENTS
• Iterative statements are decision control statements that are
used to repeat the execution of a list of statements. The
following are the types of iterative statements.
 while loop
 for loop
97
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WHILE LOOP
• The while loop provides a mechanism to repeat one or more
statements while a particular condition is true.
• Syntax:
Statement X
while (condition):
Statements block
98
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FLOWCHART FOR WHILE LOOP
99
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EXAMPLE FOR WHILE LOOP
num = 1
while num < 10:
print(num)
num = num + 3
Ouput:
1
4
7
100
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EXAMPLE FOR WHILE LOOP WITH ELSE STATEMENT
num = 10
while num > 6:
print(num)
num = num-1
else:
print("loop is finished")
Output:
10
9
8
7
loop is finished
101
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FOR LOOP
• It provides a mechanism to repeat a task until a particular
condition is true.
• It is known as determinate or definite loop because the
programmer knows exactly how many times the loop will
repeat.
Syntax 1:
for loop_control_var in sequence:
Statement block
102
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FOR LOOP CONTD..
Syntax 2:
for variable in range(beg,end,[step]):
Statements
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FLOWCHART OF FOR LOOP
104
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EXAMPLE OF FOR LOOP
numbers = [1, 2, 4, 6, 11, 20]
sq = 0
for val in numbers:
sq = val * val
print(sq)
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2/22/2022
Output:
1
4
16
36
121
400

RANGE( ) IN FOR LOOP
• range(n): generates a set of whole numbers starting
from 0 to (n-1).
For example:
range(8) is equivalent to [0, 1, 2, 3, 4, 5, 6, 7]
• range(start, stop): generates a set of whole numbers
starting from start to stop-1.
For example:
range(5, 9) is equivalent to [5, 6, 7, 8]
106
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RANGE( ) IN FOR LOOP CONTD..
• range(start, stop, step_size): The default step_size is 1
which is why when we didn’t specify the step_size, the
numbers generated are having difference of 1. However
by specifying step_size we can generate numbers having
the difference of step_size.
For example:
range(1, 10, 2) is equivalent to [1, 3, 5, 7, 9]
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EXAMPLE OF FOR LOOP WITH RANGE( )
sum = 0
for val in range(1, 6):
sum = sum + val
print(sum)
Output:
15
108
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EXAMPLE OF FOR LOOP WITH ELSE BLOCK
for val in range(5):
print(val)
else:
print("The loop has completed execution")
Output:
0
1
2
3
4
The loop has completed execution
109
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BREAK STATEMENT
• The break statement is used to terminate the
execution of the loop.
• When a compiler encounters a break statement, the
control passes to the statement that follows the loop
in which the break statement appears.
• Syntax:- break
110
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FLOWCHART FOR BREAK STATEMENT
111
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EXAMPLE FOR BREAK STATEMENT
# program to display all the elements before number 88
for num in [11, 9, 88, 10, 90, 3, 19]:
print(num)
if(num==88):
print("The number 88 is found")
print("Terminating the loop")
break
112
2/22/2022
Output:-
11
9
88
The number 88 is found
Terminating the loop

CONTINUE STATEMENT
• The continue statement can only appear in the body
of a loop.
• When a compiler encounters a continue statement,
then the rest of the statement s in the loop are skipped
and the control is unconditionally transferred to the
loop-continuation portion of the nearest loop.
• Syntax: continue
113
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FLOWCHART FOR CONTINUE STATEMENT
114
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EXAMPLE FOR CONTINUE STATEMENT
# program to display only odd numbers
for num in [20, 11, 9, 66, 4, 89, 44]:
if (num%2 == 0):
continue
print(num)
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Output
11
9
89

PASS STATEMENT
• The pass statement acts as a placeholder and usually used
when there is no need of code but a statement is still required to
make a code syntactically correct.
• Example:-
for num in [20, 11, 9, 66, 4, 89, 44]:
if num%2 == 0:
pass
else:
print(num)
Output:
11
9
89
116
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STRINGS
• String is a sequence of characters.
• String may contain alphabets, numbers and special
characters.
• String value must be enclosed within either single
quotes or within double quotes.
• String is immutable in nature. (i.e)., once created
cannot be able to edit when it is stored in a variable.
Example:
Letter = “A”
Name = ‘python’
117
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READING STRING VALUE FROM THE USER:
• Using input( ) function we can read string value from
the user.
Syntax:
Variable_name=input(“Enter the values”)
Example:
Name=input(“Enter the name”)
print(“Welcome”,name)
Output:
Enter the name: python
Welcome python
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INDEX OPERATION:
• Each character can be accessed through index operator.
Syntax:
String_variable_name[index]
• Index value starts at zero and last index value is(length of
the string-1)
Example:
119
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STRING OPERATIONS
120
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CONCATENATION OF TWO OR MORE STRINGS
• Joining of two or more strings into a single one is
called concatenation.
Syntax: String2=string1+string2
Example:
str1 = 'Hello'
str2 ='World!'
print('str1 + str2 = ', str1 + str2)
Output:
Hello World!
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REPETITION OPERATOR(*):
• It is used to concatenate the same string multiple
times.
Syntax:
String2=String1*integer value
Example:
str1 = 'Hello'
print('str1 * 3 =', str1 * 3)
Output:
HelloHelloHello
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STRING SLICING
• Slicing operations is used to select/return /slice
the particular substring based on user
requirements.
• A segment of the string is called slice.
Syntax:
String_variable_name[start:end:step value]
• Here all the parameters/variables are optional
• The default value for start is zero and end is end-1
• The default value for step is 1.
123
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EXAMPLE FOR STRING SLICING
var1 = 'Hello World!’
var2 = "Python Programming"
print "var1[0]: ", var1[0]
print "var2[1:5]: ", var2[1:5]
Output:
H
ytho
124
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STRING COMPARISON:
• We can compare two strings by using comparison
operators such as ==,!=,<,<=,>,>=.
• Python compares strings based on their corresponding
ASCII values.
• For ‘a’ASCII value is 97 and ‘A’ASCII value is 65.
125
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EXAMPLE FOR STRING COMPARISON
str1=”green”
str2=”glow”
print(“is both string are equal:”, str1==str2)
print(“is both string are not equal:”, str1!=str2)
print(“is str1>str2:”,str1>str2)
print(“is str1>str2:”,str1<str2)
126
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Output:-
is both string are equal:False
is both string are not equal:True
is str1>str2:True
is str1>str2:False

STRING ITERATION:
• We can us for loop to traverse all the characters in the
string sequentially.
• Syntax1:
for var_name in string_varaible_name:
statements
• Syntax2:
for var_name in range(initial, final,step value):
statements
127
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PROGRAM TO COUNT THE NUMBER OF
CHARACTERS IN A STRING
str=input(“enter any string:”)
count=0
for letter in str:
if(letter):
count=count+1
print(“total number of characters in string is:”, count)
Output:
Enter any string:python
Total number of characters in string is:6
128
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COUNT THE NUMBER OF CHARACTERS IN A STRING
USING RANGE FUNCTION
str=input(“enter any string:”)
count=0
for letter in range(0,len(str)+1,1):
if(letter):
count=count+1
print(“total number of characters in string is:”, count)
Output:
Enter any string: python
Total number of characters in string is:6
129
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STRING IMMUTABILITY
• Strings are immutable in nature.
• We cannot edit the string value once it is assigned to variable.
• If we try to assign or replace a value in the string, it displays
an error message that str is not a mutable object.
Program:
str= “welcome”
print(str[3])
str[3]= “c”# assigning value c to index 3 place
print(str)
Output:
c
Traceback (most recent call last):
str[3]=”c’# assigning value c to index 3 place
TypeError:’str’ object does not support item assignment
130
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STRING MODULES
• String modules contain a number of functions to
process standard python string.
• This can be done by importing string function.
Syntax:
import string
131
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LIST AS ARRAY:
• Array is a collection of similar data items that are
stored under a common name.
• Python is not providing array data type rather than it
provides a LIST.
Implementing array in python one-dimensional list:
• Arrays can be implemented as one dimensional list.
• Ex: Price_list=[70,80,90,93.5,30.456]
132
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MINIMUM VALUE IN THE LIST WITHOUT USING
INBUILT FUNCTION:
price_list=[70,80,90,93.5,30.456]
min=price_list[0]
for min_value in price_list:
if min>min_value:
min=min_value
print(“minimum value in the list is:”,min)
OUTPUT:
minimum value in the list is:34.56
133
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IMPLEMENTING ARRAY IN PYTHON AS TWO-
DIMENSIONAL LIST:
Example:
Two_dim_array_list=[[1,2],[3,4]]
Program:
two_dim=[[1,2],[3,4]]
print(“original 2 dimensional list:”)
for i in range(len(two_dim)):
for j in range(len(two_dim[i])):
print(two_dim[i][j],end=“”)
print(“n”)
134
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SQUARE ROOT OFA GIVEN NUMBER:
num=float(input("Enter a Number"))
num_sqrt=num**0.5
print("The square root of %0.3f is %0.3f"%(num,num_sqrt))
Output--
135
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GCD OF TWO NUMBERS
def gcd(a, b):
if(b==0):
return a
else:
return gcd(b, a%b)
a=int(input("Enter First number"))
b=int(input("Enter Second number"))
GCD=gcd(a, b)
print("GCD is:")
print(GCD)
2/22/2022 136

EXPONENTIATION
import math # This will import math module
print ("math.pow(100,2): ", math.pow(100,2))
print ("math.pow(100,-2): ",math.pow(100,-2))
print ("math,pow(2,4): ",math.pow(2,4))
print ("math.pow(3,0): ",math.pow(3,0))
137
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SUM AN ARRAY NUMBERS
def listsum(numlist):
sum=0
for i in numberlist:
sum=sum+i
return sum
print(listsum([1,3,5,9]))
Output:
18
138
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LINEAR SEARCH
my_data=[89,45,9,21,34]
num=int(input(“Enter search num:”))
for i in range (0, len(my_data)):
if num==my_data[i]:
print(“Item is located at position=,”i)
else:
print(“Item not found”)
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BINARY SEARCH
list=[10,20,30,40]
x=int(input(“Enter the element to search:”)
first=0
last=len(list-1)
while(first<=last):
mid=(first+last)//2
if(x==list[mid]):
print(“The element is found at the index:”,mid)
break
elif(x<list[mid]):
last=mid-1
else:
first=mid+1
else:
print(“The element is not found in the list”)
140
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VIDEO TUTORIAL
S.NO TOPIC LINK
1 Boolean Values and
Operators
https://youtu.be/7vy_GffZZTg
2 Loops in Python https://www.youtube.com/watch?v=
zFvoXxeoosI
3 Fruitful Functions https://youtu.be/hMGc19ZYzDM
4 Strings in Python https://www.youtube.com/watch?v=
QGLNQwfTO2w
5 Linear Search https://youtu.be/fHMXsGkN5cg
2/22/2022 141

SUMMARY
• Python branching statements
• Python looping statements
• Strings and its methods.
• Illustrative Programs
2/22/2022 Karpagam Institute of Technology 142

S.NO QUESTIONS BLOOMS LEVEL
1 Write a Python program to check whether a
given number is a perfect number
K3
2 Write a Python program to calculate the number
of words and number of characters present in a
string
K3
3 Write a Python code to count the occurrences of
each word in a given string sequence
K3
4 Develop a Python code to check whether a string
is palindrome or not
K5
5 Develop a Python program to detect whether
two strings are anagrams
K5
2/22/2022 143

QUIZ-TEST YOUR KNOWLEDGE
• https://docs.google.com/forms/d/e/1FAIpQLSc
Yn1TS4wfhudU0CgVwuCGlEZPQmchmz1_l
av0Q2oiONI8Gbw/viewform
2/22/2022 Karpagam Institute of Technology 144

THANK YOU
2/22/2022 145

Problem Solving and Python Programming

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