Python Programming by Dr. C. Sreedhar.pdf

Dr. C. Sreedhar, Associate Professor, CSE Dept., GPREC
PYTHON PROGRAMMING

Unit 1
 Introduction to Python Programming: Overview of Programming
Languages, History of Python, Installing Python, Executing Python Programs,
Commenting in Python, Internal Working of Python.
 Basics of Python Programming: Python Character Set, Token, Python Core
Data Type, I/O functions, Assigning Value to a Variable, Multiple
Assignments, Writing Simple Programs in Python, Formatting Number and
Strings, Python Inbuilt Functions.
 Operators and Expressions: Operators and Expressions, Arithmetic
Operators, Operator Precedence and Associativity, Changing Precedence
and Associativity of Arithmetic Operators, Translating Mathematical
Formulae into Equivalent Python Expressions, Bitwise Operator, The
Compound Assignment Operator
Dr. C. Sreedhar

Overview of Prog.Languagess
Python is a high-level general-
purpose programming language.
Translation of HLL into Machine
Language: Compiler, Interpreter
Compiler takes entire program as
input
Interpreter takes single instruction
as i/p
Guido van Rossum.
Python is interpreted
Python 3.0, released in 2008.
Machine / Low
level language
Assembly
Language
High level
Language
Compiler Interpreter

History of Python
 Invented in the Netherlands, early 90s by
Guido van Rossum
 Named after Monty Python
 Open sourced from the beginning
 Considered a scripting language, but is much more
 Scalable, object oriented and functional
 Used by Google
 Python 2.0 was released on 16 October 2000
 Python 3.0, released on 3 December 2008
 Currently Python 3.10.2 is the stable version
Dr. C. Sreedhar

Introduction to Python
 Object oriented language: Class, Object, Inheritance, Encapsulation, Polymorphism
 Interpreted language: is a layer of s/w logic b/w code and computer h/w on machine
 Supports dynamic data type: no variable declaration as in C
 Independent from platforms: Python code can run on virtually all operating systems and platforms
 Focused on development time: focuses mainly on software development and
deployment, enabling programmers to run data analysis and machine learning
 Simple and easy grammar
 Garbage collector: helps by avoiding memory leaks
 It’s free (open source)
Dr. C. Sreedhar

Installing Python
 Step 1: Visit www.python.org
 Step 2: Visit download section
 Step 3: Browse versions, latest stable version (3.10)
 Step 4: Click on Python 3.4.2 and download it
 Step 5: Double click on downloaded file
 Step 6: Click on setup
 Step 7: Click on Next (location to save)
 Step 8: Click on finish to complete installation
 Step 9: To check for python, in search box type python (Windows 10)
Dr. C. Sreedhar

Python modes
 Two modes: Command line and IDLE
 Command Line
 Press Start  Click on Python 3.4
 Click on Command line 32 bit
 IDLE

Executing Python Programs
Dr. C. Sreedhar

Commenting in Python
 # ie., hash symbol is used as a single line
comment
 ' ' ' ie., three consecutive single quotation
marks used as multiple comments or multi
line comments
Dr. C. Sreedhar

Internal working of python
Step 1: Interpreter reads python code or instruction, checks for syntax of each line
Step 2: Interpreter translates it into its equivalent form in byte code
Step 3: Byte code is sent and executed by Python Virtual Machine (PVM)
Dr. C. Sreedhar

Unit 1
 Introduction to Python Programming: Overview of Programming Languages, History of Python, Installing Python,
Executing Python Programs, Commenting in Python, Internal Working of Python.
 Basics of Python Programming: Python Character Set, Token, Python Core
Data Type, I/O functions, Assigning Value to a Variable, Multiple
Assignments, Writing Simple Programs in Python, Formatting Number and
Strings, Python Inbuilt Functions.
 Operators and Expressions: Operators and Expressions, Arithmetic
Operators, Operator Precedence and Associativity, Changing Precedence
and Associativity of Arithmetic Operators, Translating Mathematical
Formulae into Equivalent Python Expressions, Bitwise Operator, The
Compound Assignment Operator
Dr. C. Sreedhar

Python Character Set
Letters: Upper case and lower case letters
Digits: 0,1,2,3,4,5,6,7,8,9
Special Symbols: _ ( ) [ ] { } +, -, *, &, ^,
%, $, #, !, ' " " Colon(:), and Semi
Colon (;)
White Spaces: (‘tnx0bx0cr’), Space,
Tab
Dr. C. Sreedhar

Python Token
 Python has the following tokens:
 Keyword
 Identifiers
 Literals
 Operators
 Delimiters/Punctuators
Dr. C. Sreedhar

Keywords in Python 3
and except nonlocal
as finally not
assert for or
break from pass
class global raise
continue if return
def import try
del in while
elif is with
Keyword Description
and logical operator
as create an alias
assert Used in debugging
break break out of a loop
class define a class
continue
continue to the next iteration of a loop
def define a function
del delete an object
elif Used in conditional statements, same as else if
else Used in conditional statements
except Used with exceptions, what to do when an exception
occurs
false
Boolean value, result of comparison operations
Keyword Description
from To import specific parts of a module
global To declare a global variable
if To make a conditional statement
import To import a module
in To check if a value is present in a list, tuple, etc.
is To test if two variables are equal
lambda To create an anonymous function
none Represents a null value
nonlocal
To declare a non-local variable
not A logical operator
or A logical operator
pass A null statement, a statement that will do nothing
raise To raise an exception
Dr. C. Sreedhar

 Rules for Identifier:
· It consist of letters and digits in any order except that the first
character must be a letter.
· The underscore (_) counts as a character.
· Spaces are not allowed.
· Special Characters are not allowed. Such as @,$ etc.
· An identifier must not be a keyword of Python.
· Variable names should be meaningful which easily depicts the logic
Dr. C. Sreedhar

int(12.456)
12
int(‘123’)
123
type(True)
<class ‘bool’>
type(False)
<class ‘bool’>
Dr. C. Sreedhar

Python Operators
 Arithmetic operators
 Assignment operators
 Comparison operators
 Logical operators
 Identity operators
 Membership operators
 Bitwise operators
Dr. C. Sreedhar

Arithmetic Operators
+ Addition x + y
- Subtraction x - y
* Multiplication x * y
/ Division x / y
% Modulus x % y
** Exponentiation x ** y
// Floor division x // y
Assignment Operators
= X=6
+= x += 3
-= x -= 3
*= x *= 3
/= x /= 3
%= x %= 3
//= x //= 3
**= x **= 3
&= x &= 3
|= x |= 3
^= x ^= 3
>>= x >>= 3
Comparison Operators
== Equal x == y
!= Not equal x != y
> Greater than x > y
< Less than x < y
>=
Greater than or
equal to
x >= y
<=
Less than or
x <= y
Bitwise operators
& AND
| OR
^ XOR
~ NOT
<< Zero fill left shift
>> Signed right shift
Logical Operators
and x < 10 and x < 14
or x < 10 or x < 14
not not(x < 24 and x < 8)
Identity Operators
is x is y
is not x is not y

Python Core Data types
a = 10
b = 4+8j
c = 3.4
# List is an ordered sequence of items. (mutable)
li = [ 10, 2.6, 'Welcome' ]
# Tuple is ordered sequence of items(immutable)
t1 = ( 24, '4CSEA', 10+4j )
# Set is an unordered collection of unique items.
s2 = { 5,2,3,1,4 }
s4 = { 2.4, "4CSEA", (10, 20, 30) }
# Dictionary is unordered collection of key-value pairs.
d = { 'name':'Sree', 'Age':22 }
S4=“Welcome to 4CSEA”

I/O functions: print()
 print(1, 2, 3, 4) 1 2 3 4
 print(1, 2, 3, 4, sep='*') 1*2*3*4
 print(1, 2, 3, 4, sep='#', end='&') 1#2#3#4&
 print('The value of x is { } and y is { }'.format(x,y))
 print('The value of x is {0} and y is {1}'.format(x,y))
 print('The value of x is {1} and y is {0}'.format(x,y))
 print('The value of x is %3.2f ' %x)
 print('The value of x is %3.4f ' %x)
 print("a =", a, sep='0000', end='nnn')
 print(" Area of Circle is: ",format(Area,".2f"))
Dr. C. Sreedhar

I/O functions: print()
Example Output
print(format(10.345,”10.2f ”)) 10.35
print(format(10,”10.2f ”)) 10.00
print(format(10.32245,”10.2f ”)) 10.32
print(format(10.234566,”<10.2f ”)) #Left Justification Example
print(format(20,”10x”)) # Hexadecimal
print(format(20,”<10x”))
print(format(“Hello World!”,”20s”) # width
print(format(0.31456,”10.2%”)) # 31.46%
print(format(31.2345,”10.2e”)) # 3.12e+01

I/O functions: input()
Example
name = input("Enter your name: ")
inputString = input()
user_input = input()
a = int(input(“Enter your age:”))
val2 = float(input("Enter float number: "))
name, age, marks = input("Enter your Name, Age,
Percentage separated by space ").split()

Assigning Value to a Variable, Multiple
Assignments
 Assigning value to a variable
P = 100
Q = 100
R = 100
P = Q = R = 100
 Multiple assignments
P, Q = Q, P #Swap P with Q & Q with P
Dr. C. Sreedhar

Writing simple Programs in Python
 1. Program to accept student details such as name, age, rollno,
branch, semester, grade, address etc and display the same.
 2. Program to compute and print the perimeter and area of
different shapes such as rectangle, triangle, square, circle etc.,
 3. Program to check whether the given number is even or odd.
 4. Program to check whether the given integer is both divisible
by 4 and 9.
Dr. C. Sreedhar

1. Accept student details and print the same
name=input("Enter your name:")
age=int(input("Enter your age:"))
address=input("Enter your address:")
grade=float(input("Enter cgpa:"))
print('Your name is: {0}'.format(name))
print('Your age is: {0}'.format(age))
print('Your address is:
{0}'.format(address))
print('Your grade is:
{0}'.format(grade))
Dr. C. Sreedhar

2. Perimeter and area of shapes
 Rectangle
 area=l*b
 perimeter=2*(l+b)
 Triangle
 area=1/2*(b*h)
 perimeter=(s1+s2+s3)
 Square
 area=s*s
 perimeter=4*s
 Circle
 area = pi*r*r
 perimeter = 2*pi*r
Dr. C. Sreedhar

from math import pi
# Rectangle
l=int(input("Enter length of the rectangle: "))
b=int(input("Enter breadth of the rectangle: "))
area=l*b
perimeter=2*(l+b)
print("Perimeter of rectangle = " +str(perimeter))
print("Area of rectangle = " +str(area))
# Square
s=int(input("Enter side of the square: "))
area=s*s
perimeter=4*s
print("Perimeter of square = " +str(perimeter) )
print("Area of square = " +str(area))
Dr. C. Sreedhar

# Triangle
b=int(input("Enter base of the triangle: "))
h=int(input("Enter height of the triangle: "))
area=1/2*(b*h)
print("Area of rectangle = " +str(area))
s1=int(input("Enter side1 of triangle"))
perimeter=(s1+s2+s3)
print("Perimeter of rectangle = " +str(perimeter))
# Circle
r=float(input("Enter the radius of the circle:"))
print("Area of the circle is: "+str(pi*r**2))
print("Perimeter of the circle is: "+str(2*pi*r))
Dr. C. Sreedhar

3. Even or Odd
number=input("Enter a number")
x=int(number)%2
if x ==0:
print("Given number "+str(number)+" is even no.")
else:
print("Given number "+str(number)+" is odd no.“)
Dr. C. Sreedhar

4. Divisible by both
# Program to check whether given integer is both divisible by
4 and 9
number=int(input("Enter a number: "))
if((number%4==0) and (number%9==0)):
print("{0} is divisble by both 4 and 9".format(number))
else:
print("{0} is NOT divisble by both 4 and 9".format(number))
Dr. C. Sreedhar

Sum of digits using while loop
n=int(input("Enter a number:"))
tot=0
while(n>0):
dig=n%10
tot=tot+dig
n=n//10
print("The total sum of digits is:",tot)
Dr. C. Sreedhar

Multiplication table using loop
for i in range(1, 11):
print(num, '*', i, '=', num*i)
Dr. C. Sreedhar

lower = int(input("Enter start number in the range:"))
upper = int(input("Enter last number in the range:"))
print("Prime numbers between", lower, "and", upper, "are:")
for num in range(lower, upper + 1):
if num > 1:
for i in range(2, num):
if (num % i) == 0:
break
else:
print(num)
Dr. C. Sreedhar

Accept Multiline input From a User
data = [ ]
print("Enter input, press Enter twice to exit")
while True:
line = input()
if line:
data.append(line)
else:
break
finalText = 'n'.join(data)
print("n")
print("You have entered:")
print(finalText)
Dr. C. Sreedhar

PYTHON INBUILT FUNCTIONS
 X = int(input()) #Convert it to int
X = float(input()) #Convert it to float
 The full form of eval function is to evaluate. It takes a string as
parameter and returns it as if it is a Python expression.
 eval(‘print(“Hello”)’)
 print(format(10.234566,”10.2f”)) #Right Justification Example
 print(format(10.234566,”<10.2f”)) #Left Justification Example
 print(format(20,”10x”)) #Integer formatted to Hexadecimal
Integer
 print(format(20,”<10x”))
Dr. C. Sreedhar

 Formatting Scientific Notation
 print(format(31.2345,”10.2e”))
 3.12e+01
 print(format(131.2345,”10.2e”))
 1.31e+02
Dr. C. Sreedhar

PYTHON INBUILT FUNCTIONS
 abs(x) Returns absolute value of x
 Example: abs(-2) returns 2
 abs(4) returns 4
 tan(X) : Return the tangent of X, where X is the value in radians
 math.tan(3.14/4)
 0.9992039901050427
 degrees(X) : Convert angle X from to radians to degrees
 math.degrees(1.57)
 89.95437383553924
 Radians(X) >>> math.
 radians(89.99999)
 1.5707961522619713
Dr. C. Sreedhar

High-level data types
 Numbers: int, long, float, complex
 Strings: immutable
 Lists and dictionaries: containers
 Other types for e.g. binary data, regular expressions,
introspection
 Extension modules can define new “built-in” data types
Dr. C. Sreedhar

History of Python
 Created in 1990 by Guido van Rossum
 Named after Monty Python
 First public release in 1991
 comp.lang.python founded in 1994
 Open source from the start
Dr. C. Sreedhar

Python features
no compiling or linking rapid development cycle
no type declarations simpler, shorter, more flexible
automatic memory management garbage collection
high-level data types and operations fast development
object-oriented programming code structuring and reuse, C++
embedding and extending in C mixed language systems
classes, modules, exceptions "programming-in-the-large" support
dynamic loading of C modules simplified extensions, smaller binaries
dynamic reloading of C modules programs can be modified without
stopping
Dr. C. Sreedhar

Python features
universal "first-class" object model fewer restrictions and rules
run-time program construction handles unforeseen needs, end-user
coding
interactive, dynamic nature incremental development and testing
access to interpreter information metaprogramming, introspective objects
wide portability cross-platform programming without
ports
compilation to portable byte-code execution speed, protecting source code
built-in interfaces to external services system tools, GUIs, persistence,
databases, etc.
Dr. C. Sreedhar

Where to use python?
 System management (i.e., scripting)
 Graphic User Interface (GUI)
 Internet programming
 Database (DB) programming
 Text data processing
 Distributed processing
 Numerical operations
 Graphics
 And so on…
Dr. C. Sreedhar

 Google in its web search systems
 YouTube video sharing service is largely written in Python.
 BitTorrent peer-to-peer file sharing system.
 Google’s popular App Engine web development framework
uses Python as its application language.
 EVE Online, a Massively Multiplayer Online Game (MMOG).
 Maya, a powerful integrated 3D modeling and animation
system, provides a Python scripting API.
Dr. C. Sreedhar

 Intel, Cisco, Hewlett-Packard, Seagate, Qualcomm, and IBM use
Python for hardware testing.
 Industrial Light & Magic, Pixar, and others use Python in the
production of animated movies.
 JPMorgan Chase, UBS, Getco, and Citadel apply Python for
financial market forecasting.
 NASA, Los Alamos, Fermilab, JPL, and others use Python for
scientific programming tasks.
 iRobot uses Python to develop commercial robotic devices.
Dr. C. Sreedhar

 ESRI uses Python as an end-user customization tool for its
popular GIS mapping products.
 NSA uses Python for cryptography and intelligence analysis.
 The IronPort email server product uses more than 1 million lines
of Python code to do its job.
 The One Laptop Per Child (OLPC) project builds its user
interface and activity model in Python.
Dr. C. Sreedhar

Strings
 "hello"+"world" "helloworld" # concatenation
 "hello"*3 "hellohellohello" # repetition
 "hello"[0] "h" # indexing
 "hello"[-1] "o" # (from end)
 "hello"[1:4] "ell" # slicing
 len("hello") 5 # size
 "hello" < "jello" 1 # comparison
 "e" in "hello" 1 # search
 "escapes: n etc, 033 etc, if etc"
 'single quotes' """triple quotes""" r"raw strings"
Dr. C. Sreedhar

Lists
 Flexible arrays, not Lisp-like linked lists
 a = [99, "bottles of beer", ["on", "the", "wall"]]
 Same operators as for strings
 a+b, a*3, a[0], a[-1], a[1:], len(a)
 Item and slice assignment
 a[0] = 98
 a[1:2] = ["bottles", "of", "beer"]
-> [98, "bottles", "of", "beer", ["on", "the", "wall"]]
 del a[-1] # -> [98, "bottles", "of", "beer"]
Dr. C. Sreedhar

Dictionaries
 Hash tables, "associative arrays"
 d = {"duck": "eend", "water": "water"}
 Lookup:
 d["duck"] -> "eend"
 d["back"] # raises KeyError exception
 Delete, insert, overwrite:
 del d["water"] # {"duck": "eend", "back": "rug"}
 d["back"] = "rug" # {"duck": "eend", "back": "rug"}
 d["duck"] = "duik" # {"duck": "duik", "back": "rug“}
Dr. C. Sreedhar

Tuples
 key = (lastname, firstname)
 point = x, y, z # parentheses optional
 x, y, z = point # unpack
 lastname = key[0]
 singleton = (1,) # trailing comma!!!
 empty = () # parentheses!
 tuples vs. lists; tuples immutable
Dr. C. Sreedhar

Variables
 No need to declare
 Need to assign (initialize)
 use of uninitialized variable raises exception
 Not typed
if friendly: greeting = "hello world"
else: greeting = 12**2
print greeting
 Everything is a "variable":
 Even functions, classes, modules
Dr. C. Sreedhar

Comments
 Syntax:
# comment text (one line)
swallows2.py
1
2
3
4
5
6
# Suzy Student, CSE 142, Fall 2097
# This program prints important messages.
print("Hello, world!")
print() # blank line
print("Suppose two swallows "carry" it together.")
print('African or "European" swallows?')
Dr. C. Sreedhar

Functions
 Function: Equivalent to a static method in Java.
 Syntax:
def name():
statement
statement
...
statement
 Must be declared above the 'main' code
 Statements inside the function must be indented
hello2.py
1
2
3
4
5
6
7
# Prints a helpful message.
def hello():
# main (calls hello twice)
hello()
hello()
Dr. C. Sreedhar

Whitespace Significance
 Python uses indentation to indicate blocks, instead of {}
 Makes the code simpler and more readable
 In Java, indenting is optional. In Python, you must indent.
hello3.py
1
2
3
4
5
6
7
8
# Prints a helpful message.
def hello():
print("How are you?")
# main (calls hello twice)
hello()
hello()
Dr. C. Sreedhar

Python’s Core Data Types
 Numbers: Ex: 1234, 3.1415, 3+4j, Decimal, Fraction
 Strings: Ex: 'spam', "guido's", b'ax01c'
 Lists: Ex: [1, [2, 'three'], 4]
 Dictionaries: Ex: {'food': 'spam', 'taste': 'yum'}
 Tuples: Ex: (1, 'spam', 4, 'U')
 Files: Ex: myfile = open('eggs', 'r')
 Sets: Ex: set('abc'), {'a', 'b', 'c'}
Dr. C. Sreedhar

Builtin Data type: Number
 >>> 123 + 222 # Integer addition
 345 >>> 1.5 * 4 # Floating-point multiplication 6.0
 >>> 2 ** 100 # 2 to the power 100
1267650600228229401496703205376
 >>> 3.1415 * 2 # repr: as code 6.2830000000000004
 >>> print(3.1415 * 2) # str: user-friendly 6.283
Dr. C. Sreedhar

Builtin Data type: Number
 >>> import math
 >>> math.pi 3.1415926535897931
 >>> math.sqrt(85
 >>> import random
 >>> random.random() 0.59268735266273953
 >>> random.choice([1, 2, 3, 4]) 1) 9.2195444572928871
Dr. C. Sreedhar

Builtin Data type: String
 Strings are used to record textual information
 strings are sequences of one-character strings; other types of
sequences include lists and tuples.
 >>> S = 'Spam'
 >>> len(S) # Length 4
 >>> S[0] # The first item in S, indexing by zero-based position 'S'
 >>> S[1] # The second item from the left 'p'
 >>> S[-1] # The last item from the end in S 'm'
 >>> S[-2] # The second to last item from the end 'a'
Dr. C. Sreedhar

 >>> S[-1] # The last item in S 'm'
 >>> S[len(S)-1] # Negative indexing, the hard way 'm'
 >>> S # A 4-character string 'Spam'
 >>> S[1:3] # Slice of S from offsets 1 through 2 (not 3) 'pa'
Dr. C. Sreedhar

 >>> S[1:] # Everything past the first (1:len(S)) 'pam'
 >>> S # S itself hasn't changed 'Spam'
 >>> S[0:3] # Everything but the last 'Spa'
 >>> S[:3] # Same as S[0:3] 'Spa'
 >>> S[:-1] # Everything but the last again, but simpler (0:-1)
'Spa'
 >>> S[:] # All of S as a top-level copy (0:len(S)) 'Spam'
Dr. C. Sreedhar

 >>> S Spam'
 >>> S + 'xyz' # Concatenation
 'Spamxyz'
 >>> S # S is unchanged 'Spam'
 >>> S * 8 # Repetition
'SpamSpamSpamSpamSpamSpamSpamSpam'
Dr. C. Sreedhar

 Immutable:
 immutable in Python—they cannot be changed in-place after they
are created.
 >>> S 'Spam'
 >>> S[0] = 'z' # Immutable objects cannot be changed ...error text
omitted... TypeError: 'str' object does not support item assignment
 >>> S = 'z' + S[1:] # But we can run expressions to make new
objects
 >>> S 'zpam'
Dr. C. Sreedhar

 >>> S.find('pa') # Find the offset of a substring 1
 >>> S 'Spam'
 >>> S.replace('pa', 'XYZ') # Replace occurrences of a
substring with another 'SXYZm'
 >>> S 'Spam'
Dr. C. Sreedhar

 >>> line = 'aaa,bbb,ccccc,dd'
 >>> line.split(',') # Split on a delimiter into a list of substrings ['aaa',
'bbb', 'ccccc', 'dd']
 >>> S = 'spam'
 >>> S.upper() # Upper- and lowercase conversions 'SPAM'
 >>> S.isalpha() # Content tests: isalpha, isdigit, etc. True
 >>> line = 'aaa,bbb,ccccc,ddn'
 >>> line = line.rstrip() # Remove whitespace characters on the right side
 >>> line 'aaa,bbb,ccccc,dd'
Dr. C. Sreedhar

 >>> '%s, eggs, and %s' % ('spam', 'SPAM!') # Formatting
expression (all) 'spam, eggs, and SPAM!'
 >>> '{0}, eggs, and {1}'.format('spam', 'SPAM!') # Formatting
method (2.6, 3.0) 'spam, eggs, and SPAM!'
Dr. C. Sreedhar

 >>> S = 'AnBtC' # n is end-of-line, t is tab >>> len(S) #
Each stands for just one character 5
 >>> ord('n') # n is a byte with the binary value 10 in ASCII
10
 >>> S = 'A0B0C' # 0, a binary zero byte, does not
terminate string
 >>> len(S) 5
Dr. C. Sreedhar

Pattern Matching
 to do pattern matching in Python, we import a module called
re.
 This module has analogous calls for searching, splitting, and
replacement.
 >>> import re
 >>> match = re.match('Hello[ t]*(.*)world', 'Hello Python
world')
 >>> match.group(1) 'Python '
Dr. C. Sreedhar

Python vs. Java
 Code 5-10 times more concise
 Dynamic typing
 Much quicker development
 no compilation phase
 less typing
 Yes, it runs slower
 but development is so much faster!
 Similar (but more so) for C/C++
 Use Python with Java: JPython!
Dr. C. Sreedhar

Installing Python: Linux/Ubuntu
 Install Python 3.6:
 1. To follow the installation procedure, you need to be connected to the Internet.
 2. Open the terminal by pressing Ctrl + Alt + T keys together.
 3. Install Python 3.6:
 a. For Ubuntu 16.04 and Ubuntu 17.04:
 i. In the terminal, run the command sudo apt-get install python3.6
 ii. Press Enter.
 iii. The terminal will prompt you for your password, type it in to the terminal.
 iv. Press Enter.
 b. For Ubuntu 17.10 and above, the system already comes with Python 3.6installed by default.
 To check Python is installed or not, open terminal and enter command: python3 --version
Dr. C. Sreedhar

Installing Python: Windows
 Install Python 3.6:
 1. To follow the installation procedure, you need to be connected to the Internet.
 2. Visit https://www.python.org/downloads/release/python-368/
 3. At the bottom locate Windows x86-64 executable installer for 64 bits OS and
 Windows x86 executable installer for 32 bits OS
 4. Click on the located installer file to download.
 5. After download completes, double click on the installer file to start the
installation procedure.
 6. Follow the instructions as per the installer
Dr. C. Sreedhar

Executing Python Programs
 Linux
 Open text editor, type the source code and save the program with .py
extension (Ex: ex1.py)
 Open terminal, run the command python
 Run the program using the command, python ex1.py
 Google Colab
 Instructions to execute python program is sent to your official email id
 Jupyter Notebook
 Run Jupyter Notebook and copy paste URL in the browser
 Type the source code in the cell and press CTRL+Enter
Dr. C. Sreedhar

Unit 2
 Decision Statements: Boolean Type, Boolean Operators, Using
Numbers with Boolean Operators, Using String with Boolean
Operators, Boolean Expressions and Relational Operators,
Decision Making Statements, Conditional Expressions.
 Loop Control Statements: while Loop, range() Function, for Loop,
Nested Loops, break, continue.
 Functions: Syntax and Basics of a Function, Use of a Function,
Parameters and Arguments in a Function, The Local and Global
Scope of a Variable, The return Statement, Recursive Functions,
The Lambda Function.
Dr. C. Sreedhar

Boolean type
Python boolean data type has two values: True and False.
bool() function is used to test if a value is True or False.
a = True
type(a)
bool
b = False
type(b)
bool
branch = "CSE"
sem = 4
section =''
print(bool(branch))
print(bool(sem))
print(bool(section))
print(bool(["app", “bat", “mat"]))
True
True
False
True
Dr. C. Sreedhar

Boolean operators
not
and
or
A=True
B=False
print(A and B)
print(A or B)
print(not A)
False
True
False
A=True
B=False
C=False
D= True
print((A and D) and (B or C))
print((A and D) or (B or C))
False
True
Dr. C. Sreedhar

Write code that counts the number of words in
sentence that contain either an “a” or an “e”.
sentence=input()
words = sentence.split(" ")
count = 0
for i in words:
if (('a' in i) or ('e' in i)) :
count +=1
print(count)
Welcome to Computer Science and Engineering
5
Dr. C. Sreedhar

BOOLEAN EXPRESSIONS AND RELATIONAL
OPERATORS
2 < 4 or 2
True
2 < 4 or [ ]
True
5 > 10 or 8
8
print(1 <= 1)
print(1 != 1)
print(1 != 2)
print("CSEA" != "csea")
print("python" != "python")
print(123 == "123")
True
False
True
True
False
False
Dr. C. Sreedhar

x = 84
y = 17
print(x >= y)
print(y <= x)
print(y < x)
print(x <= y)
print(x < y)
print(x % y == 0)
True
True
True
False
False
False
x = True
y = False
print(not y)
print(x or y)
print(x and not y)
print(not x)
print(x and y)
print(not x or y)
True
True
True
False
False
False
Dr. C. Sreedhar

Decision statements
Python supports the following decision-
making statements.
if statements
if-else statements
Nested if statements
Multi-way if-elif-else statements
Dr. C. Sreedhar

if
 Write a program that prompts a user to enter two integer values.
Print the message ‘Equals’ if both the entered values are equal.
 if num1- num2==0: print(“Both the numbers entered are Equal”)
 Write a program which prompts a user to enter the radius of a circle.
If the radius is greater than zero then calculate and print the area
and circumference of the circle
if Radius>0:
Area=Radius*Radius*pi
.........
Dr. C. Sreedhar

 Write a program to calculate the salary of a medical
representative considering the sales bonus and incentives
offered to him are based on the total sales. If the sales
exceed or equal to 1,00,000 follow the particulars of
Column 1, else follow Column 2.
Dr. C. Sreedhar

Sales=float(input(‘Enter Total Sales of the Month:’))
if Sales >= 100000:
basic = 4000
hra = 20 * basic/100
da = 110 * basic/100
incentive = Sales * 10/100
bonus = 1000
conveyance = 500
else:
basic = 4000
hra = 10 * basic/100
da = 110 * basic/100
incentive = Sales * 4/100
bonus = 500
conveyance = 500
salary= basic+hra+da+incentive+bonus+conveyance
# print Sales,basic,hra,da,incentive,bonus,conveyance,sal
Dr. C. Sreedhar

Write a program to read three numbers from a user and
check if the first number is greater or less than the other
two numbers.
if num1>num2:
if num2>num3:
print(num1,”is greater than “,num2,”and “,num3)
else:
print(num1,” is less than “,num2,”and”,num3)
Dr. C. Sreedhar

Finding the Number of Days in a Month
flag = 1
month = (int(input(‘Enter the month(1-12):’)))
if month == 2:
year = int(input(‘Enter year:’))
if (year % 4 == 0) and (not(year % 100 == 0)) or (year % 400 == 0):
num_days = 29
else:
num_days = 28
elif month in (1,3,5,7,8,10,12):
num_days = 31
elif month in (4, 6, 9, 11):
num_days = 30
else:
print(‘Please Enter Valid Month’)
flag = 0
if flag == 1:
print(‘There are ‘,num_days, ‘days in’, month,’ month’)
Dr. C. Sreedhar

Write a program that prompts a user to enter two different
numbers. Perform basic arithmetic operations based on the
choices.
.......
if choice==1:
print(“ Sum=,”is:”,num1+num2)
elif choice==2:
print(“ Difference=:”,num1-num2)
elif choice==3:
print(“ Product=:”,num1*num2)
elif choice==4:
print(“ Division:”,num1/num2)
else:
print(“Invalid Choice”)
Dr. C. Sreedhar

Multi-way if-elif-else Statements: Syntax
If Boolean-expression1:
statement1
elif Boolean-expression2 :
statement2
elif Boolean-expression3 :
statement3
- - - - - - - - - - - - - -
- - - - - - - - - - - -- -
elif Boolean-expression n :
statement N
else :
Statement(s)
Dr. C. Sreedhar

CONDITIONAL EXPRESSIONS
if x%2==0:
x = x*x
else:
x = x*x*x
x=x*x if x % 2 == 0 else x*x*x
min=print(‘min=‘,n1) if n1<n2 else print(‘min = ‘,n2)
a=int(input(“Enter number: “)
print(‘even’) if(a%2) ==0 else print(‘Odd’)
Dr. C. Sreedhar

Loop Controlled Statements
while Loop
range() Function
for Loop
Nested Loops
break Statement
continue Statement
Dr. C. Sreedhar

Multiplication table using while in reverse order
num=int(input("Enter no: "))
count = 10
while count >= 1:
prod = num * count
print(num, "x", count, "=", prod)
count = count - 1
Enter no: 4
4 x 10 = 40
4 x 9 = 36
4 x 8 = 32
4 x 7 = 28
4 x 6 = 24
4 x 5 = 20
4 x 4 = 16
4 x 3 = 12
4 x 2 = 8
4 x 1 = 4
Dr. C. Sreedhar

num=int(input(“Enter the number:”))
fact=1
ans=1
while fact<=num:
ans*=fact
fact=fact+1
print(“Factorial of”,num,” is: “,ans)
Factorial of a given number
Dr. C. Sreedhar

text = "Engineering"
for character in text:
print(character)
E
n
g
i
n
e
e
r
i
n
g
courses = ["Python", "Computer Networks", "DBMS"]
for course in courses:
print(course)
Python
Computer Networks
DBMS
Dr. C. Sreedhar

for i in range(10,0,-1):
print(i,end=" ")
# 10 9 8 7 6 5 4 3 2 1
range(start,stop,step size)
Dr. C. Sreedhar

Program which iterates through integers from 1 to 50 (using for loop).
For an integer that is even, append it to the list even numbers.
For an integer that is odd, append it the list odd numbers
even = []
odd = []
for number in range(1,51):
if number % 2 == 0:
even.append(number)
else:
odd.append(number)
print("Even Numbers: ", even)
print("Odd Numbers: ", odd)
Even Numbers: [2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50]
Odd Numbers: [1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49]
Dr. C. Sreedhar

matrix=[]
for i in range(2):
row=[]
for j in range(2):
num=int(input())
row.append(num)
matrix.append(row)
print(matrix)
Accept matrix elements and display
Dr. C. Sreedhar

for i in range(1,100,1):
if(i==11):
break
else:
print(i, end=” “)
1 2 3 4 5 6 7 8 9 10
break
Dr. C. Sreedhar

for i in range(1,11,1):
if i == 5:
continue
print(i, end=” “)
1 2 3 4 6 7 8 9 10
continue
Dr. C. Sreedhar

def square(num):
return num**2
print (square(2))
print (square(3))
Function: Example
Dr. C. Sreedhar

def disp_values(a,b=10,c=20):
print(“ a = “,a,” b = “,b,”c= “,c)
disp_values(15)
disp_values(50,b=30)
disp_values(c=80,a=25,b=35)
a = 15 b = 10 c= 20
a = 50 b = 30 c= 20
a = 25 b = 35 c= 80
Dr. C. Sreedhar

LOCAL AND GLOBAL SCOPE OF A VARIABLE
p = 20 #global variable p
def Demo():
q = 10 #Local variable q
print(‘Local variable q:’,q)
print(‘Global Variable p:’,p)
Demo()
print(‘global variable p:’,p)
Local variable q: 10
Global Variable p: 20
global variable p: 20
Dr. C. Sreedhar

a = 20
def Display():
a = 30
print(‘a in function:’,a)
Display()
print(‘a outside function:’,a)
a in function: 30
a outside function: 20
Dr. C. Sreedhar

Write a function calc_Distance(x1, y1, x2, y2) to calculate the distance
between two points represented by Point1(x1, y1) and Point2 (x2, y2).
The formula for calculating distance is:
import math
def EuclD (x1, y1, x2, y2):
dx=x2-x1
dx=math.pow(dx,2)
dy=y2-y1
dy=math.pow(dy,2)
z = math.pow((dx + dy), 0.5)
return z
print("Distance = ",(format(EuclD(4,4,2,2),".2f")))
Dr. C. Sreedhar

def factorial(n):
if n==0:
return 1
return n*factorial(n-1)
print(factorial(4))
Dr. C. Sreedhar

def test2():
return 'cse4a', 68, [0, 1, 2]
a, b, c = test2()
print(a)
print(b)
print(c) cse4a
68
[0, 1, 2]
Returning multiple values
Dr. C. Sreedhar

def factorial(n):
if n < 1:
return 1
else:
return n * factorial(n-1)
print(factorial(4))
Recursion: Factorial
Dr. C. Sreedhar

def power(x, y):
if y == 0:
return 1
else:
return x * power(x,y-1)
power(2,4)
Recursion: power(x,y)
Dr. C. Sreedhar

A lambda function is a small anonymous function with no name.
Lambda functions reduce the number of lines of code
when compared to normal python function defined using def
lambda function
(lambda x: x + 1)(2) #3
(lambda x, y: x + y)(2, 3) #5
Dr. C. Sreedhar

Unit 4
 Exceptions: When Something Goes Wrong, Classes of
Exceptions, A Final Note on Pythonic Exception Handling.
 File Handling: Need of File Handling, Text Input and Output,
The seek() Function, Binary Files, Accessing and Manipulating
Files and Directories on a Disk.
 Modules: Reusing Code with Modules and Packages,
Understanding Python Modules, Everyday Module Usage,
Advanced Module Behavior, Combining Modules into Packages
Dr. C. Sreedhar

Unit 4
• Modules: Reusing Code with Modules and Packages,
Understanding Python Modules, Everyday Module
Usage, Advanced Module Behavior, Combining
Modules into Packages
• Exceptions: When Something Goes Wrong, Classes of
Exceptions, A Final Note on Pythonic Exception
Handling.
• File Handling: Need of File Handling, Text Input and
Output, The seek() Function, Binary Files, Accessing
and Manipulating Files and Directories on a Disk.
Dr. C. Sreedhar

• os
– os.getcwd()
– os.fspath(path)
– os.getlogin()
• ipaddress:
–ipaddress.IPv4Address(addres
s)
–ipaddress.IPv6Address(addres
s)
• math:
– math.factorial(x)
– math.gcd(n1,n2)
– math.lcm(n1,n2)
– math.trunc(x)
– math.pow(x, y)
– math.pi
• random:
– random.randint(a,b)
– random.uniform(a,b)
• time:
– time.clock_gettime()
– time.clock_gettime_ns(
)
Module: Builtin Modules
Dr. C. Sreedhar

Modules: Create and import
• 1. Open Python IDLE (Start --> Python IDLE)
• 2. File --> New File
• 3. ---- type the following code----
def greeting(name):
print("Hello, " + name)
• 4. Save with module1.py (in Desktop or any folder)
• 5. Pyhton IDLE ==> File --> New File
• 6. ------ type the following code ----
import module1
module1.greeting("CSE4A")
• 7. Save as runmodule.py (in Desktop or any folder)
• 8. In Python IDLE, click on Run --> Run Module
from <module_name> import *
from <module_name> import <name> as
<alt_name>
Dr. C. Sreedhar

module2.py
----------------------------------------------
def sum_list(lst):
print('Sum=',sum(lst))
---------------------------------------------
summodule.py
---------------------------------------------
import module2
l1=[10,20,30,40]
module2.sum_list(l1)
Modules: Create and import
Dr. C. Sreedhar

In python, the inbuilt __import__() function helps to import modules
in runtime
Syntax:
__import__(name, globals, locals, fromlist, level)
Ex:
math_score = __import__('math', globals(), locals(), [],
0)
print(math_score.fabs(17.4))
Dr. C. Sreedhar

Package
• A package is basically a directory with Python
file and file with the extension as _init_.py.
• Steps to create package:
– create a package (folder). The name of package, say, My _ First _ Package
– Create _ init _ .py file inside the created package My_First_Package.
– The directory should contain a file named _init_.py. This file can be empty or
it may contain valid Python code.
– create two different .py files, i.e. a.py and b.py with code
a.py
def call_A():
print(“This is first
program”)
b.py
def call_B():
print(“This is second”)
>>> My_First_Package.a.call_A()
This is first program
>>> My_First_Package.b.call_B()
This is second
_init_.py
import My_First_Package.a
import My_First_Package.b
Dr. C. Sreedhar

# GPREC/CSBS/__init__.py (Empty
file)
# GPREC/CSBS/csbs4sem.py
print("In CSBS branch")
# GPREC/CSE/__init__.py
from . import cse4a
from . import cse4b
# GPREC/CSE/cse4a.py
print("In CSE 4A Class")
# GPREC/CSE/cse4b.py
print("In CSE 4B Class")
# GPREC/CSE/cse4c.py
print("In CSE 4C Class")
# world/__init__.py
from . import CSBS
from GPREC import CSE
import GPREC.CSE.cse4a
from GPREC.CSE import cse4b
Dr. C. Sreedhar

Exceptions
• An exception is an event, which occurs during the execution of a program,
that disrupts the normal flow of the program's instructions.
• Exception: Base class for all exceptions
• ArithmeticError: Base class for all errors that occur for numeric calculation.
• OverflowError: Raised when a calculation exceeds maximum limit for a numeric type.
• FloatingPointError: Raised when a floating point calculation fails.
• ZeroDivisionError: Raised when division or modulo by zero takes place for numeric
• AttributeError: Raised in case of failure of attribute reference or assignment.
• EOFError: Raised when end of file is reached.
• ImportError: Raised when an import statement fails.
• IndexError: Raised when an index is not found in a sequence.
• EnvironmentError: Base class for all exceptions that occur outside Python
environment.
• SyntaxError: Raised when there is an error in Python syntax.
• TypeError: Raised when an operation is attempted that is invalid for specified data type.
Dr. C. Sreedhar

try:
<body>
except <ExceptionType1>:
<handler1>
except <ExceptionTypeN>:
<handlerN>
except:
<handlerExcept>
else:
<process_else>
finally:
<process_finally>
Dr. C. Sreedhar

try:
num1,num2 = eval(input("Enter two numbers,separated by a comma:"))
result = num1 / num2
print("Result is", result)
except ZeroDivisionError:
print("Division by zero is error !!")
except SyntaxError:
print("Comma is missing. Enter nos separated by comma like this 1,
2")
except:
print("Wrong input")
else:
print("No exceptions")
finally:
print("This will execute no matter what“)
Dr. C. Sreedhar

try:
a = [1, 2, 3]
print (a[3])
except LookupError:
print ("Index out of bound error.")
else:
print ("Success")
Dr. C. Sreedhar

try:
age= int(input())
assert (age>0 and age<100)
# True: moves to the next line ie., print age; False: returns Assertion Error
except AssertionError:
print("Not valid age.")
except:
print("Invalid data entered")
else:
print("Age is:",age)
Dr. C. Sreedhar

try:
age= int(input("Enter your age:"))
if age<0:
raise ValueError
except ValueError:
print("Age cannot be less than zero.")
else:
print("Age is:",age)
Dr. C. Sreedhar

Format:
<file variable> = open(<file name>, "r")
Example:
filename = input("Enter name of input file: ")
inputFile = open(filename, "r")
Python File handling Dr. C. Sreedhar

Modes Description
r Opens a file for reading only, default mode.
rb Opens a file for reading only in binary format.
r+ Opens a file for both reading and writing
rb+ Opens a file for both reading and writing in binary format
w Opens a file for writing only. Overwrites the file if the file exists.
Wb Opens a file for writing only in binary format. Overwrites the file if the file
exists
w+ Opens a file for both writing and reading, Overwrites file if file
exists
Dr. C. Sreedhar

Example:
file2 = open(“cse4a.txt", "wb")
print ("Name of the file: ", file2.name)
print ("Closed or not : ", file2.closed)
print ("Opening mode : ", file2.mode)
This would produce following result:
Name of the file: foo.txt
Closed or not : False
Opening mode : wb
Dr. C. Sreedhar

Reading contents from file
inputFileName = input("Enter name of input file:")
inputFile = open(inputFileName, "r")
print("Opening file", inputFileName, " for reading.")
for line in inputFile:
sys.stdout.write(line)
inputFile.close()
print("Completed reading of file", inputFileName)
Dr. C. Sreedhar

Alternate way to read contents from file
inputFileName = input ("Enter name of input file: ")
line = inputFile.readline()
while (line != ""):
sys.stdout.write(line)
line = inputFile.readline()
inputFile.close()
print("Completed reading of file", inputFileName)
Dr. C. Sreedhar

Writing contents
fo = open(“cse4a.txt", "wb")
fo.write("Welcome to CSE4A n");
fo.close()
Dr. C. Sreedhar

Writing contents from one file into
another
inputFileName = input("Enter file name to read grades from:
")
outputFileName = input("output filename to write GPA's to:
")
outputFile = open(outputFileName, "w")
print("Opening file", outputFileName, " for writing.")
gpa = 0
Dr. C. Sreedhar

seek()
• seek() function is used to change the
position of the File Handle to a given
specific position.
Dr. C. Sreedhar

Python Programming by Dr. C. Sreedhar.pdf

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