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PYTHON PROGRAMMING
UNIT-I:

Python Introduction
• Python is a dynamic, high level, free open source and interpreted
programming language. It supports object-oriented programming
as well as procedural oriented programming.
• Python is a programming language that includes features of C and
Java. It provides the style of writing an elegant code like C, and for
object-oriented programming, it offers classes and objects like
Java.
• It was created by Guido van Rossum, and released in 1991.
• Python is commonly used for developing websites and software,
game development, data analysis, and data visualization.
2

Python Interpreter
• Machines only understand machine code or machine language, a
language represented by strings of bits — 1s and 0s.
• A python interpreter is a computer program that converts each
high-level program statement into machine code.
• An interpreter translates the command that you write out into
code that the computer can understand.
• Python is the most famous example of a high-level language.
3

Features of Python
1. Free and Open Source:
• Python language is freely available at the official website and you
can download it. Since it is open-source, this means that source
code is also available to the public. So you can download it, use it
as well as share it.
2. Easy to code:
• Python is a high-level programming language. Python is very easy
to learn the language as compared to other languages like C, C#,
Javascript, Java, etc. It is very easy to code in the Python
language and anybody can learn Python basics in a few hours or
days. It is also a developer-friendly language.
4

Features of Python
3. Easy to Read:
• Python’s syntax is straightforward. The code block is defined by the
indentations rather than by semicolons or brackets.
4. Object-Oriented Language:
• One of the key features of Python is Object-Oriented programming.
Python supports object-oriented language and concepts of classes,
object encapsulation, etc.
5. GUI Programming Support:
• Graphical User interfaces can be made using a module such
as PyQt5, PyQt4, wxPython, or Tk in Python. PyQt5 is the most
popular option for creating graphical apps with Python.
5

Features of Python
6. High-Level Language:
• Python is a high-level language. When we write programs in
Python, we do not need to remember the system architecture, nor
do we need to manage the memory.
7. Large Community Support:
• Python has gained popularity over the years. Our questions are
constantly answered by the enormous StackOverflow community.
8. Easy to Debug:
• Excellent information for mistake tracing. You will be able to quickly
identify and correct the majority of your program’s issues once you
understand how to interpret Python’s error traces.
6

Features of Python
9. Python is a Portable language:
• If we have Python code for Windows and if we want to run this code
on other platforms such as Linux, Unix, and Mac then we do not need
to change it, we can run this code on any platform.
10. Python is an Integrated language:
• Python is also an Integrated language because we can easily integrate
Python with other languages like C, C++, etc.
11. Interpreted Language:
• Python is an Interpreted Language because Python code is executed
line by line at a time. like other languages C, C++, Java, etc. there is no
need to compile Python code this makes it easier to debug our code.
The source code of Python is converted into an immediate form
called bytecode. 7

Features of Python
12. Large Standard Library:
• Python has a large standard library that provides a rich set of modules
and functions so you do not have to write your own code for every
single thing. There are many libraries present in Python such as regular
expressions, unit-testing, web browsers, etc.
13. Dynamically Typed Language:
• Python is a dynamically-typed language. That means the type for a
variable is decided at run time not in advance because of this feature
we don’t need to specify the type of variable.
15. Allocating Memory Dynamically:
• In Python, the variable data type does not need to be specified. The
memory is automatically allocated to a variable at runtime when it is
given a value. 8

Python Installation
• Download Python Executable Installer from www.python.org
9

First Python Program Execution
1) Interactive Mode Programming
• Invoking the interpreter without passing a script file as a
parameter brings up the following prompt
10

First Python Program Execution
2) Script Mode Programming
• Invoking the interpreter with a script parameter begins execution
of the script and continues until the script is finished. When the
script is finished, the interpreter is no longer active.
• Let us write a simple Python program in a script. Python files
have extension .py. Type the following source code in a test.py
file −
• print ("Hello, Python!“)
11

Python Indentation
• Indentation refers to the spaces at the beginning of a code line.
• Where in other programming languages the indentation in code
is for readability only, the indentation in Python is very
important.
• Python uses indentation to indicate a block of code.
• Example
• if 5>2:
print("Five is greater than two!")
12

Python Comment
• Comments can be used to explain Python code.
• Comments can be used to make the code more readable.
• Comments can be used to prevent execution when testing code.
• Creating a Comment: Comments starts with a #, and Python will
ignore them.
• Example
• #This is a comment
print("Hello, World!")
13

Python Multi Line Comment
• To add a multiline comment:
1. insert a # for each line.
2. you can add a multiline string (triple quotes) in your code, and
place your comment inside it
• Example
• """
This is a comment
written in
more than just one line
"""
print("Hello, World!")
14

Python Variables
• Variables are containers for storing data values.
• Unlike other programming languages, Python has no command
for declaring a variable.
• A variable is created the moment you first assign a value to it.
• Variables do not need to be declared with any particular type and
can even change type after they have been set.
• Example: Assign Value to Variable
• x = 5
y = "John"
print(x)
print(y)
15

Python Identifiers
• Identifier is a user-defined name given to a variable, function,
class, module, etc.
• The identifier is a combination of character digits and an
underscore.
• They are case-sensitive i.e., ‘num’ and ‘Num’ and ‘NUM’ are
three different identifiers.
16

Python Identifiers
• Rules for Naming Python Identifiers
1. It cannot be a reserved python keyword.
2. It should not contain white space.
3. It can be a combination of A-Z, a-z, 0-9, or underscore.
4. It should start with an alphabet character or an underscore ( _ ).
5. It should not contain any special character other than an
underscore ( _ ).
17

Python Examples of Python Identifiers
• Example
• #Legal names:
myvar = "John"
my_var = "John"
_my_var = "John"
myVar = "John"
MYVAR = "John"
myvar2 = "John“
• #Illegal names:
2myvar = "John"
my-var = "John"
my var = "John"
18

Python Operators
• Operators in general are used to perform operations on values
and variables. These are standard symbols used for the purpose
of logical and arithmetic operations.
• OPERATORS: These are the special symbols. Eg- + , * , /, etc.
• OPERAND: It is the value on which the operator is applied.
• Types of Operators in Python
1. Arithmetic Operators
2. Comparison Operators
3. Logical Operators
4. Bitwise Operators
5. Assignment Operators
6. Identity Operators and Membership Operators
19

Python Arithmetic Operators
20
Operator Description Syntax
+ Addition: adds two operands x + y
– Subtraction: subtracts two operands x – y
* Multiplication: multiplies two operands x * y
/
Division (float): divides the first operand by
the second
x / y
//
Division (floor): divides the first operand by
the second
x // y
%
Modulus: returns the remainder when the
first operand is divided by the second
x % y
** Power: Returns first raised to power second x ** y

Python Comparison Operators
21
>
Greater than: True if the left operand is greater than the
right
x > y
< Less than: True if the left operand is less than the right x < y
== Equal to: True if both operands are equal x == y
!= Not equal to – True if operands are not equal x != y
>=
Greater than or equal to True if the left operand is greater
than or equal to the right
x >= y
<=
Less than or equal to True if the left operand is less than or
equal to the right
x <= y

Python Logical Operators
22
and Logical AND: True if both the operands are true x and y
Or Logical OR: True if either of the operands is true x or y
not Logical NOT: True if the operand is false not x

Python Bitwise Operators
23
& Bitwise AND x & y
| Bitwise OR x | y
~ Bitwise NOT ~x
^ Bitwise XOR x ^ y
>> Bitwise right shift x>>
<< Bitwise left shift x<<

Python Assignment Operators
24
= Assign the value of the right side of the expression to the left side operand x = y + z
+=
Add AND: Add right-side operand with left-side operand and then assign to left
operand
a+=b a=a+b
-=
Subtract AND: Subtract right operand from left operand and then assign to left
operand
a-=b a=a-b
*=
Multiply AND: Multiply right operand with left operand and then assign to left
operand
a*=b a=a*b
/= Divide AND: Divide left operand with right operand and then assign to left operand a/=b a=a/b
%=
Modulus AND: Takes modulus using left and right operands and assign the result to
left operand
a%=b a=a%b
//=
Divide(floor) AND: Divide left operand with right operand and then assign the
value(floor) to left operand
a//=b a=a//b
**=
Exponent AND: Calculate exponent(raise power) value using operands and assign
value to left operand
a**=b a=a**b

Python Identity Operators
• In Python, is and is not are the identity operators both are used to
check if two values are located on the same part of the memory.
• Two variables that are equal do not imply that they are identical.
• is : True if the operands are identical
• is not: True if the operands are not identical
25

Python Membership Operators
• In Python, in and not in are the membership operators that are used
to test whether a value or variable is in a sequence.
• in :True if value is found in the sequence
• not in :True if value is not found in the sequence
26

Python Operator Precedence
27
Operator Description Operator Description
** Exponentiation I Bitwise OR
+x, -x Positive, negative <, , >=, !=, == Comparison operators
*, /, //, %
Multiplication, division, floor
division, modulo
is, is not Identity operators
+, – Addition, subtraction in, not in Membership operators
<> Bitwise shift operators not Logical NOT
& Bitwise AND and Logical AND
^ Bitwise XOR or Logical OR

Python Operator Precedence
1) x = 7 + 3 * 2
Ans: 13
2) x = 5 + 3 * 2 ** 2 // 4
Ans: 8
3) x = 6 + 3 * 2 – 1
Ans:?
28

Python Data Types
• Variables can store data of different types, and different types can do
different things.
• Python has the following data types built-in by default, in these
categories:
1. Text Type: str
2. Numeric Types: int, float, complex
3. Sequence Types: list, tuple, range
4. Mapping Type: dict
5. Set Types: set, frozenset
6. Boolean Type: bool
29

Python Data Types
• Getting the Data Type:
• You can get the data type of any object by using the type() function:
• Example: Print the data type of the variable x:
x = 5
print(type(x))
Output:
<class 'int'>
30

Python Data Types
31
Example Data Types
x = "Hello World" str
x = 20 int
x = 20.5 float
x = 1j complex
x = ["apple", "banana", "cherry"] list
x = ("apple", "banana", "cherry") tuple
x = range(6) range
x = {"name" : "John", "age" : 36} dict
x = {"apple", "banana", "cherry"} set
x = frozenset({"apple", "banana", "cherry"}) frozenset
x = True bool

Python Strings
• A String is a data structure in Python that represents a sequence of
characters.
• It is an immutable data type, meaning that once you have created a
string, you cannot change it.
• Strings are used widely in many different applications, such as storing
and manipulating text data, representing names, addresses, and
other types of data that can be represented as text.
• Python does not have a character data type, a single character is
simply a string with a length of 1.
32

Python Strings
Creating a String in Python:
• Strings in Python can be created using single quotes or double
quotes or even triple quotes. Let us see how we can define a string in
Python.
Example:
String1 = 'Welcome to DSU‘
print(String1)
Output:
Welcome to DSU
33

Python String Indexing
• Accessing characters in Python String (String Indexing)
• In Python, individual characters of a String can be accessed by using
the method of Indexing.
• Indexing allows negative address references to access characters
from the back of the String, e.g. -1 refers to the last character, -2
refers to the second last character, and so on.
• While accessing an index out of the range will cause an IndexError.
• Only Integers are allowed to be passed as an index, float or other
types that will cause a TypeError.
34

36
Example:
String1 = "GeeksForGeeks"
print("Initial String: ")
print(String1)
print("nFirst character of String is: ")
print(String1[0])
print("nLast character of String is: ")
print(String1[-1])
Output:
Initial String:
GeeksForGeeks
First character of String is:
G
Last character of String is:
s

• Reversing a Python String:
• By accessing characters from a string, we can also reverse strings in
Python.
• We can Reverse a string by using String slicing method.
37
Example:
str = "geeksforgeeks"
print(str[::-1])
Output:
skeegrofskeeg

Python String Slicing
• String Slicing:
• In Python, the String Slicing method is used to access a range of
characters in the String.
• Slicing in a String is done by using a Slicing operator, i.e., a colon (:).
• String returned after slicing includes the character at the start index
but not the character at the last index.
• In this example, we will use the string-slicing method to extract a
substring of the original string. The [3:12] indicates that the string
slicing will start from the 3rd index of the string to the 12th index,
(12th character not including). We can also use negative indexing in
string slicing.
38

Python String Slicing
39
Example:
String1 = "GeeksForGeeks"
print(String1)
print("nSlicing characters from 3-12: ")
print(String1[3:12])
print("nSlicing characters between " +
"3rd and 2nd last character: ")
print(String1[3:-2])
Output:
Initial String:
GeeksForGeeks
Slicing characters from 3-12:
ksForGeek
Slicing characters between 3rd and 2nd
last character:
ksForGee

Python String
• Deleting from a String:
• In Python, the Updation or deletion of characters from a String is not
allowed.
• This will cause an error because item assignment or item deletion
from a String is not supported.
• Although deletion of the entire String is possible with the use of a
built-in del keyword.
• This is because Strings are immutable, hence elements of a String
cannot be changed once assigned. Only new strings can be
reassigned to the same name.
40

Python String
• Updating a character
• A character of a string can be updated in Python by first converting
the string into a Python List and then updating the element in the
list.
• As lists are mutable in nature, we can update the character and then
convert the list back into the String.
• Another method is using the string slicing method. Slice the string
before the character you want to update, then add the new
character and finally add the other part of the string again by string
slicing.
41

Python String
42
# Python Program to Update character of a String
String1 = "Hello, I'm a Geek"
print(String1)
list1 = list(String1)
list1[2] = 'p'
String2 = ''.join(list1)
print("nUpdating character at 2nd Index: ")
print(String2)
String3 = String1[0:2] + 'p' + String1[3:]
print(String3)
Output:
Initial String:
Hello, I'm a Geek
Updating character at 2nd Index:
Heplo, I'm a Geek
Heplo, I'm a Geek

Python String
• Updating Entire String:
• As Python strings are immutable in nature, we cannot update the
existing string. We can only assign a completely new value to the
variable with the same name.
43
print(String1)
String1 = "Welcome to the Geek World"
print("nUpdated String: ")
print(String1)
Output:
Initial String:
Hello, I'm a Geek
Updated String:
Welcome to the Geek World

Python String
• Deleting a character
• Python strings are immutable, that means we cannot delete a
character from it. When we try to delete the character using
the del keyword, it will generate an error.
• So we will first slice the string up to the character that we want to
delete and then concatenate the remaining string next from the
deleted character.
44

Python String
45
Example:
print(String1)
String2 = String1[0:2] + String1[3:]
print("nDeleting character at 2nd
Index: ")
print(String2)
Output:
Initial String:
Hello, I'm a Geek
Deleting character at 2nd Index:
Helo, I'm a Geek

Python String Escape Sequences
• Escape Sequencing in Python:
• While printing Strings with single and double quotes in it
causes SyntaxError because String already contains Single and
Double Quotes and hence cannot be printed with the use of either of
these.
• Hence, to print such a String either Triple Quotes are used or Escape
sequences are used to print Strings.
• Escape sequences start with a backslash and can be interpreted
differently.
• If single quotes are used to represent a string, then all the single
quotes present in the string must be escaped and the same is done
for Double Quotes.
46

47
String1 = '''I'm a "Geek"'''
print("Initial String with use of Triple Quotes: ")
print(String1)
# Escaping Single Quote
String1 = 'I'm a "Geek"'
print("nEscaping Single Quote: ")
print(String1)
# Escaping Double Quotes
String1 = "I'm a "Geek""
print("nEscaping Double Quotes: ")
print(String1)
# Printing Paths with the use of Escape Sequences
String1 = "C:PythonGeeks"
print("nEscaping Backslashes: ")
print(String1)
# Printing Paths with the use of Tab
String1 = "HitGeeks"
print("nTab: ")
print(String1)
# Printing Paths with the use of New Line
String1 = "PythonnGeeks"
print("nNew Line: ")
print(String1)
Output:
Initial String with use of Triple Quotes:
I'm a "Geek"
Escaping Single Quote:
I'm a "Geek"
Escaping Double Quotes:
I'm a "Geek"
Escaping Backslashes:
C:PythonGeeks
Tab:
Hi Geeks
New Line:
Python
Geeks

48
String1 = '''I'm a "Geek"'''
print("Initial String with use of Triple Quotes: ")
print(String1)
# Escaping Single Quote
String1 = 'I'm a "Geek"'
print("nEscaping Single Quote: ")
print(String1)
# Escaping Double Quotes
String1 = "I'm a "Geek""
print("nEscaping Double Quotes: ")
print(String1)
# Printing Paths with the use of Escape Sequences
String1 = "C:PythonGeeks"
print("nEscaping Backslashes: ")
print(String1)
# Printing Paths with the use of Tab
String1 = "HitGeeks"
print("nTab: ")
print(String1)
# Printing Paths with the use of New Line
String1 = "PythonnGeeks"
print("nNew Line: ")
print(String1)
Output:
Initial String with use of Triple Quotes:
I'm a "Geek"
Escaping Single Quote:
I'm a "Geek"
Escaping Double Quotes:
I'm a "Geek"
Escaping Backslashes:
C:PythonGeeks
Tab:
Hi Geeks
New Line:
Python
Geeks

Python Conditionals
• Python supports the usual logical conditions from mathematics :
These conditions can be used in several ways, most commonly in "if
statements" and loops.
• Equals: a == b
• Not Equals: a != b
• Less than: a < b
• Less than or equal to: a <= b
• Greater than: a > b
• Greater than or equal to: a >= b
49

Python If Condition
• An "if statement" is written by using the if keyword.
• Example of If statement:
• a = 33
b = 200
if b > a:
print("b is greater than a")
• Output:
• b is greater than a
50

Python Elif Condition
• The elif keyword is Python's way of saying "if the previous
conditions were not true, then try this condition".
• Example
• a = 33
b = 33
if b > a:
elif a == b:
print("a and b are equal")
51

Python Else Condition
• The else keyword catches anything which isn't caught by the
preceding conditions.
• Example
• a = 200
b = 33
if b > a:
elif a == b:
print("a and b are equal")
else:
print("a is greater than b")
52

Python And Condition
• The and keyword is a logical operator, and is used to combine
conditional statements:
• Example
• Test if a is greater than b, AND if c is greater than a:
• a = 200
b = 33
c = 500
if a > b and c > a:
print("Both conditions are True")
• Output:
• Both conditions are True
53

Python Or Condition
• The or keyword is a logical operator, and is used to combine
conditional statements:
• Example
• Test if a is greater than b, OR if a is greater than c:
• a = 200
b = 33
c = 500
if a > b or a > c:
print("At least one of the conditions is True")
• Output:
• At least one of the conditions is True
54

Python not Condition
• The not keyword is a logical operator, and is used to reverse the
result of the conditional statement:
• Example
• Test if a is NOT greater than b:
• a = 33
b = 200
if not a > b:
print("a is NOT greater than b")
• Output:
• a is NOT greater than b
55

Python Nested if Condition
• You can have if statements inside if statements, this is called nested
if statements.
• Example
• x = 41
if x > 10:
print("Above ten,")
if x > 20:
print("and also above 20!")
else:
print("but not above 20.")
• Output:
• Above ten,
and also above 20! 56

Python Loops
• A loop is an instruction that repeats multiple times as long as some
condition is met.
• Types of Python Loops:
• While Loop
• For Loop
• Break Statement
57

While Loop
• The while loop is used to execute a set of statements as long as a
condition is true.
58

While Loop
• While Loop Syntax:
while expression:
statement(s)
59
Example:
count = 0
while (count < 3):
count = count + 1
print("Hello GM")
Output:
Hello GM
Hello GM
Hello GM

For Loop
• A for loop in Python is used to iterate over a sequence (list, tuple,
set, dictionary, and string).
60

For Loop
• For Loop Syntax:
for iterator_var in sequence:
statements(s)
61
Example:
n = 4
for i in range(0, n):
print(i)
Output:
0 1 2 3

Nested Loop
• Python programming language allows to use one loop inside another
loop which is called nested loop.
• Nested Loops Syntax:
statements(s)
statements(s)
62

Nested Loop
63
Example:
#outer loop
for i in range(1, 11):
# nested loop
# to iterate from 1 to 10
for j in range(1, 11):
# print multiplication
print(i * j, end=' ')
print()
Output:
1 2 3 4 5 6 7 8 9 10
2 4 6 8 10 12 14 16 18 20
3 6 9 12 15 18 21 24 27 30
4 8 12 16 20 24 28 32 36 40
5 10 15 20 25 30 35 40 45 50
6 12 18 24 30 36 42 48 54 60
7 14 21 28 35 42 49 56 63 70
8 16 24 32 40 48 56 64 72 80
9 18 27 36 45 54 63 72 81 90
10 20 30 40 50 60 70 80 90 100

Continue Statement
• The continue statement in Python returns the control to the
beginning of the loop.
64
Example:
for letter in 'geeksfor':
if letter == 'e' or letter == 's':
continue
print('Current Letter :', letter)
Output:
Current Letter : g
Current Letter : k
Current Letter : f
Current Letter : o
Current Letter : r

Break Statement
• The break statement in Python brings control out of the loop.
65
Example:
for letter in 'geeksforgeeks':
if letter == 'e' or letter == 's':
break
print('Current Letter :', letter)
Output:
Current Letter : e

Pass Statement
• We use pass statement in Python to write empty loops. Pass is also
used for empty control statements, functions and classes.
• Example: This Python code iterates through the characters of the
string ‘geeksforgeeks’ using a ‘for' loop. However, it doesn’t perform
any specific action within the loop, and the ‘pass' statement is used.
After the loop, it prints “Last Letter :” followed by the last character
in the string, which is ‘s’.
66
Example:
for letter in 'geeksforgeeks':
pass
print('Last Letter :', letter)
Output:
Last Letter : s

Questions From Unit-1
1) Explain Features of Python Programming Language.
2) Explain different types of comments in Python.
3) What is Variable? How to assign Value to variable in python?
4) What is Python identifier? Write rules for naming the identifiers. Give some examples
of legal names of identifiers.
5) What are Python Operators? Explain Types of operators in detail with example.
6) What is difference between == and ‘is’ operator in python?
7) Explain Built-in data types of python.
8) What is string in python? Explain String Indexing and slicing with example.
9) Explain Escape Sequences in python.
10)Explain if, elif and else with example.
11)Explain while loop and for loop with syntax and example.
12)Explain usage of continue, break and pass keyword in python.
67

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