CLASS-XI

SUBJECT: COMPUTERSCIENCE(083)– PYTHON

CHAPTER
CHAPTERNAME
NO.

1 INTRODUCTION TO PYTHON

2 PYTHONFUNDAMENTALS

3 DATAHANDLING

4 FLOW OF CONTROL

5 FUNCTIONSIN PYTHON

6 STRING IN PYTHON

7 LIST IN PYTHON

8 TUPLE IN PYTHON

9 DICTIONARY IN PYTHON

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 CHAPTER-1
INTRODUTION TO PYTHON
1.1 Introduction:
➢ General-purpose Object Oriented Programming language.
➢ High-level language
➢ Developed in late 1980 by Guido van Rossum at National Research Institute for
Mathematics and Computer Science in the Netherlands.
➢ It is derived from programming languages such as Modula 3, small talk, Algol-68.
➢ It is Open Source Scripting language.
➢ It is Case-sensitive language (Difference between uppercase and lowercase letters).
➢ One of the official languages at Google.

1.2 Characteristics of Python:

✓ Interpreted: Python source code is compiled to byte code as a .pyc file, and this byte
code can be interpreted by the interpreter.
✓ Interactive
✓ Object Oriented Programming Language
✓ Easy & Simple
✓ Portable
✓ Scalable: Provides improved structure for supporting large programs.
✓ Integrated
✓ Expressive Language
1.3 Python Interpreter:
Names of some Python interpreters are:
▪ PyCharm
▪ Python IDLE
▪ The Python Bundle
▪ pyGUI
▪ Sublime Text etc.

There are two modes to use the python interpreter:

i. Interactive Mode
ii. Script Mode

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i. Interactive Mode: Without passing python script file to the interpreter, directly
execute code to Python (Command line).

Example:
>>>6+3

Output: 9

Fig: Interactive Mode

Note: >>> is a command the python interpreter uses to indicate that it is ready. The
interactive mode is better when a programmer deals with small pieces of code.
To run a python file on command line:
exec(open(“C:\Python33\python programs\program1.py”).read( ))

ii. Script Mode: In this mode source code is stored in a file with the .py extension
and use the interpreter to execute the contents of the file. To execute the script by the
interpreter, you have to tell the interpreter the name of the file.

Example:
if you have a file name Demo.py , to run the script you have to follow the following
steps:

Step-1: Open the text editor i.e. Notepad

Step-2: Write the python code and save the file with .py file extension. (Default
directory is C:\Python33/Demo.py)
Step-3: Open IDLE ( Python GUI) python shell
Step-4: Click on file menu and select the open option
Step-5: Select the existing python file
Step-6: Now a window of python file will be opened
Step-7: Click on Run menu and the option Run Module.

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Step-8: Output will be displayed on python shell window.

Fig. : IDLE (Python GUI)

Fig: Python Shell

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 CHAPTER-2
PYTHONFUNDAMENTALS

2.1 Python Character Set :

It is a set of valid characters that a language recognize.
Letters: A-Z, a-z
Digits : 0-9
Special Symbols
Whitespace

2.2 TOKENS
Token: Smallest individual unit in a program is known as token.
There are five types of token in python:
1. Keyword
2. Identifier
3. Literal
4. Operators
5. Punctuators

1. Keyword: Reserved words in the library of a language. There are 33 keywords in

python.

False class finally, is return break

None continue for lambda try except

True def from nonlocal while in

and del global not with raise

as elif if or yield

assert else import pass

All the keywords are in lowercase except 03 keywords (True, False, None).

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2. Identifier: The name given by the user to the entities like variable name, class-name,
function-name etc.

Rules for identifiers:

▪ It can be a combination of letters in lowercase (a to z) or uppercase (A to Z) or

digits (0 to 9) or an underscore.
▪ It cannot start with a digit.
▪ Keywords cannot be used as an identifier.
▪ We cannot use special symbols like !, @, #, $, %, + etc. in identifier.
▪ _ (underscore) can be used in identifier.
▪ Commas or blank spaces are not allowed within an identifier.

3. Literal: Literals are the constant value. Literals can be defined as a data that is given in
a variable or constant.

Literal

String Literal
Numeric Boolean Special
Collections

int float complex

True False None

A. Numeric literals: Numeric Literals are immutable.

Eg.

5, 6.7, 6+9j

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B. String literals:

String literals can be formed by enclosing a text in the quotes. We can use both single as
well as double quotes for a String.

Eg:

"Aman" , '12345'

Escape sequence characters:

\\ Backslash
\’ Single quote
\” Double quote
\a ASCII Bell
\b Backspace
\f ASCII Formfeed
\n New line charater
\t Horizontal tab

C. Boolean literal: A Boolean literal can have any of the two values: True or False.

D. Special literals: Python contains one special literal i.e. None.

None is used to specify to that field that is not created. It is also used for end of lists in
Python.

E. Literal Collections: Collections such as tuples, lists and Dictionary are used in Python.

4. Operators: An operator performs the operation on operands. Basically there are two
types of operators in python according to number of operands:
A. Unary Operator
B. Binary Operator

A. Unary Operator: Performs the operation on one operand.

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 Example:
+ Unary plus
- Unary minus
~ Bitwise complement
not Logical negation

B. Binary Operator: Performs operation on two operands.

5. Separator or punctuator : , ; , ( ), { }, [ ]

2.3 Mantissaand Exponent Form:

A real number in exponent form has two parts:

➢ mantissa
➢ exponent
Mantissa : It must be either an integer or a proper real constant.
Exponent : It must be an integer. Represented by a letter E or e followed by integer value.

Valid Exponent form Invalid Exponent form

123E05 2.3E (No digit specified for exponent)
1.23E07
0.24E3.2 (Exponent cannot have fractional part)
0.123E08
23,455E03 (No comma allowed)
123.0E08
123E+8
1230E04
-0.123E-3
163.E4
.34E-2
4.E3

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2.4 Basic terms of a Python Programs:
A. Blocks and Indentation
B. Statements
C. Expressions
D. Comments

A. Blocks and Indentation:

• Python provides no braces to indicate blocks of code for class and function definition or
flow control.
• Maximum line length should be maximum 79 characters.
• Blocks of code are denoted by line indentation, which is rigidly enforced.
• The number of spaces in the indentation is variable, but all statements within the block
must be indented the same amount.
for example –
if True:
print(“True”)
else:
print(“False”)

B. Statements
A line which has the instructions or expressions.

C. Expressions:
A legal combination of symbols and values that produce a result. Generally it produces a value.

D. Comments: Comments are not executed. Comments explain a program and make a
program understandable and readable. All characters after the # and up to the end of the
physical line are part of the comment and the Python interpreter ignores them.

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There are two types of comments in python:
i. Single line comment
ii. Multi-line comment

i. Single line comment: This type of comments start in a line and when a line ends, it is
automatically ends. Single line comment starts with # symbol.
Example: if a>b: # Relational operator compare two values

ii. Multi-Line comment: Multiline comments can be written in more than one lines. Triple
quoted ‘ ’ ’ or “ ” ”) multi-line comments may be used in python. It is also known as
docstring.
Example:
‘’’ This program will calculate the average of 10 values.
First find the sum of 10 values
and divide the sum by number of values
‘’’

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Multiple Statements on a Single Line:
The semicolon ( ; ) allows multiple statements on the single line given that neither statement
starts a new code block.
Example:-
x=5; print(“Value =” x)

2.5 Variable/Label in Python:

Definition: Named location that refers to a value and whose value can be used and processed
during program execution.
Variables in python do not have fixed locations. The location they refer to changes every time
their values change.

Creating a variable:

A variable is created the moment you first assign a value to it.

Example:

x=5

y = “hello”

Variables do not need to be declared with any particular type and can even change type after
they have been set. It is known as dynamic Typing.

x = 4 # x is of type int
x = "python" # x is now of type str
print(x)

Rules for Python variables:

• A variable name must start with a letter or the underscore character

• A variable name cannot start with a number
• A variable name can only contain alpha-numeric characters and underscore (A-z, 0-9,
and _ )
• Variable names are case-sensitive (age, Age and AGE are three different variables)

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Python allows assign a single value to multiple variables.

Example: x=y=z=5

You can also assign multiple values to multiple variables. For example −

x , y , z = 4, 5, “python”
4 is assigned to x, 5 is assigned to y and string “python” assigned to variable z respectively.
x=12
y=14
x,y=y,x
print(x,y)
Now the result will be
14 12

Lvalue and Rvalue:

An expression has two values. Lvalue and Rvalue.
Lvalue: the LHS part of the expression
Rvalue: the RHS part of the expression
Python first evaluates the RHS expression and then assigns to LHS.
Example:
p, q, r= 5, 10, 7
q, r, p = p+1, q+2, r-1
print (p,q,r)
Now the result will be:
6 6 12

Note: Expressions separated with commas are evaluated from left to right and assigned in same
order.

❖ If you want to know the type of variable, you can use type( ) function :

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Syntax:
type (variable-name)
Example:
x=6
type(x)
The result will be:
<class ‘int’>
❖ If you want to know the memory address or location of the object, you can use id( )
function.
Example:
>>>id(5)
1561184448
>>>b=5
>>>id(b)
1561184448
You can delete single or multiple variables by using del statement. Example:
del x
del y, z

2.6 Input from a user:

input( ) method is used to take input from the user.
Example:
print("Enter your name:")
x = input( )
print("Hello, " + x)

➢ input( ) function always returns a value of string type.

2.7 Type Casting:

To convert one data type into another data type.

Casting in python is therefore done using constructor functions:

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 • int( ) - constructs an integer number from an integer literal, a float literal or a string
literal.

Example:

x = int(1) # x will be 1
y = int(2.8) # y will be 2
z = int("3") # z will be 3

• float( ) - constructs a float number from an integer literal, a float literal or a string literal.

Example:

x = float(1) # x will be 1.0

y = float(2.8) # y will be 2.8
z = float("3") # z will be 3.0
w = float("4.2") # w will be 4.2

• str( ) - constructs a string from a wide variety of data types, including strings, integer
literals and float literals.

Example:

x = str("s1") # x will be 's1'

y = str(2) # y will be '2'
z = str(3.0) # z will be '3.0'

Reading a number from a user:

x= int (input(“Enter an integer number”))

2.8 OUTPUT using print( ) statement:

Syntax:
print(object, sep=<separator string >, end=<end-string>)

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object : It can be one or multiple objects separated by comma.
sep : sep argument specifies the separator character or string. It separate the objects/items. By
default sep argument adds space in between the items when printing.
end : It determines the end character that will be printed at the end of print line. By default it
has newline character( ‘\n’ ).
Example:
x=10
y=20
z=30
print(x,y,z, sep=’@’, end= ‘ ‘)
Output:
10@20@30

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 CHAPTER-3
DATAHANDLING
3.1 Data Types in Python:
Python has Two data types –
1. Primitive Data Type (Numbers, String)
2. Collection Data Type (List, Tuple, Set, Dictionary)

Data Types

Primitive Collection
Data Type Data Type

Number String

List Tuple Set Dictionary

int float complex

1. Primitive Data Types:

a. Numbers: Number data types store numeric values.

There are three numeric types in Python:

• int
• float
• complex

Example:
w=1 # int
y = 2.8 # float
z = 1j # complex

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• integer : There are two types of integers in python:
➢ int
➢ Boolean

➢ int: int or integer, is a whole number, positive or negative, without decimals.

Example:

x=1
y = 35656222554887711
z = -3255522
➢ Boolean: It has two values: True and False. True has the value 1 and False has the
value 0.
Example:

>>>bool(0)
False
>>>bool(1)
True
>>>bool(‘ ‘)
False
>>>bool(-34)
True
>>>bool(34)
True

• float : float or "floating point number" is a number, positive or negative, containing one
or more decimals. Float can also be scientific numbers with an "e" to indicate the power
of 10.
Example:

x = 1.10
y = 1.0
z = -35.59
a = 35e3
b = 12E4
c = -87.7e100
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 • complex : Complex numbers are written with a "j" as the imaginary part.
Example:

>>>x = 3+5j
>>>y = 2+4j
>>>z=x+y
>>>print(z)
5+9j
>>>z.real
5.0
>>>z.imag
9.0
Real and imaginary part of a number can be accessed through the attributes real and imag.

b. String: Sequence of characters represented in the quotation marks.

▪ Python allows for either pairs of single or double quotes. Example: 'hello' is the same
as "hello" .
▪ Python does not have a character data type, a single character is simply a string with a
length of 1.
▪ The python string store Unicode characters.
▪ Each character in a string has its own index.
▪ String is immutable data type means it can never change its value in place.

2. Collection Data Type:

➢ List
➢ Tuple
➢ Set
➢ Dictionary

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3.2 MUTABLE & IMMUTABLE Data Type:
➢ Mutable Data Type:
These are changeable. In the same memory address, new value can be stored.
Example: List, Set, Dictionary
➢ Immutable Data Type:
These are unchangeable. In the same memory address new value cannot be stored.
Example: integer, float, Boolean, string and tuple.

3.3 Basic Operators in Python:

i. Arithmetic Operators
ii. Relational Operator
iii. Logical Operators
iv. Bitwise operators
v. Assignment Operators
vi. Other Special Operators
o Identity Operators
o Membership operators

i. Arithmetic Operators: To perform mathematical operations.

RESULT
OPERATOR NAME SYNTAX
(X=14, Y=4)

+ Addition x+y 18

_ Subtraction x–y 10

* Multiplication x*y 56

/ Division (float) x/y 3.5

// Division (floor) x // y 3

% Modulus x%y 2

** Exponent x**y 38416

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 Example:
>>>x= -5
>>>x**2
>>> -25

ii. Relational Operators: Relational operators compare the values. It either

returns True or False according to the condition.

RESULT
OPERATOR NAME SYNTAX
(IF X=16, Y=42)

False
> Greater than x>y
True
< Less than x<y
False
== Equal to x == y
True
!= Not equal to x != y
False
>= Greater than or equal to x >= y
True
<= Less than or equal to x <= y

iii. Logical operators: Logical operators perform Logical AND, Logical OR and Logical
NOT operations.

OPERATOR DESCRIPTION SYNTAX

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 operand is false not x

Examples of Logical Operator:

The and operator: The and operator works in two ways:

a. Relational expressions as operands
b. numbers or strings or lists as operands

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a. Relational expressions as operands:

X Y X and Y
False False False
False True False
True False False
True True True

>>> 5>8 and 7>3

False
>>> (4==4) and (7==7)
True

b. numbers or strings or lists as operands:

In an expression X and Y, if first operand has false value, then return first operand X as a
result, otherwise returns Y.
X Y X and Y
>>>0 and 0
0 false false X
>>>0 and 6 false true X
0 true false Y
>>>‘a’ and ‘n’ true true Y
’n’
>>>6>9 and ‘c’+9>5 # and operator will test the second operand only if the first operand
False # is true, otherwise ignores it, even if the second operand is wrong

The or operator: The or operator works in two ways:

a. Relational expressions as operands
b. numbers or strings or lists as operands

a. Relational expressions as operands:

X Y X or Y
False False False
False True True
True False True
True True True

>>> 5>8 or 7>3

True
>>> (4==4) or (7==7)
True

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b. numbers or strings or lists as operands:
In an expression X or Y, if first operand has true value, then return first operand X as a
result, otherwise returns Y.

X Y X or Y
false false Y
false true Y
true false X
true true X

>>>0 or 0
0
>>>0 or 6
6
>>>‘a’ or ‘n’
’a’
>>>6<9 or ‘c’+9>5 # or operator will test the second operand only if the first operand
True # is false, otherwise ignores it, even if the second operand is wrong

The not operator:

>>>not 6
False
>>>not 0
True
>>>not -7
False

Chained Comparison Operators:

>>> 4<5>3 is equivalent to >>> 4<5 and 5>3
True True

iv. Bitwise operators: Bitwise operators acts on bits and performs bit by bit operation.

OPERATOR DESCRIPTION SYNTAX

& Bitwise AND x&y

| Bitwise OR x|y

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 ~ Bitwise NOT ~x

^ Bitwise XOR x^y

>> Bitwise right shift x>>

<< Bitwise left shift x<<

Examples:
Let Output:
a = 10 0
b=4
14
print(a & b) -11
print(a | b) 14
2
print(~a)
40
print(a ^ b)
print(a >> 2)

print(a << 2)

v. Assignment operators: Assignment operators are used to assign values to the variables.

OPERA
TOR DESCRIPTION SYNTAX

= Assign value of right side of expression to left side operand x=y+z

Add AND: Add right side operand with left side operand and a+=b
+=
then assign to left operand a=a+b
Subtract AND: Subtract right operand from left operand and then a-=b a=a-
-=
assign to left operand b
Multiply AND: Multiply right operand with left operand and then a*=b
*=
assign to left operand a=a*b
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 Divide AND: Divide left operand with right operand and then a/=b
/=
assign to left operand a=a/b
Modulus AND: Takes modulus using left and right operands and a%=b
%=
assign result to left operand a=a%b
Divide(floor) AND: Divide left operand with right operand and a//=b
//=
then assign the value(floor) to left operand a=a//b
Exponent AND: Calculate exponent(raise power) value using a**=b
**=
operands and assign value to left operand a=a**b
Performs Bitwise AND on operands and assign value to left a&=b
&=
operand a=a&b
Performs Bitwise OR on operands and assign value to left a|=b
|=
operand a=a|b
Performs Bitwise xOR on operands and assign value to left a^=b
^=
operand a=a^b
Performs Bitwise right shift on operands and assign value to left a>>=b
>>=
operand a=a>>b
Performs Bitwise left shift on operands and assign value to left a <<=b a=
<<=
operand a << b
vi. Other Special operators: There are some special type of operators like-

a. Identity operators- 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
does not imply that they are identical.
is True if the operands are identical
is not True if the operands are not identical

Example:
Let
a1 = 3
b1 = 3
a2 = 'PythonProgramming'
b2 = 'PythonProgramming'
a3 = [1,2,3]
b3 = [1,2,3]

print(a1 is not b1)

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print(a2 is b2) # Output is False, since lists are mutable.
print(a3 is b3)

Output:
False
True
False
Example:
>>>str1= “Hello”
>>>str2=input(“Enter a String :”)
Enter a String : Hello
>>>str1==str2 # compares values of string
True
>>>str1 is str2 # checks if two address refer to the same memory address
False

b. Membership operators- in and not in are the membership operators; 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

Example:
Let
x = 'Digital India'
y = {3:'a',4:'b'}

print('D' in x)

print('digital' not in x)

print('Digital' not in x)

print(3 in y)

print('b' in y)

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Output:
True
True
False
True
False

3.4 Operator Precedence and Associativity:

Operator Precedence: It describes the order in which operations are performed when an
expression is evaluated. Operators with higher precedence perform the operation first.
Operator Associativity: whenever two or more operators have the same precedence, then
associativity defines the order of operations.

Operator Description Associativity Precedence

( ), { } Parentheses (grouping) Left to Right
f(args…) Function call Left to Right
x[index:index] Slicing Left to Right
x[index] Subscription Left to Right
** Exponent Right to Left
~x Bitwise not Left to Right
+x, -x Positive, negative Left to Right
*, /, % Product, division, remainder Left to Right
+, – Addition, subtraction Left to Right
<<, >> Shifts left/right Left to Right
& Bitwise AND Left to Right
^ Bitwise XOR Left to Right
| Bitwise OR Left to Right
<=, <, >, >= Comparisons Left to Right
=, %=, /=, += Assignment
is, is not Identity
in, not in Membership
not Boolean NOT Left to Right
and Boolean AND Left to Right
or Boolean OR Left to Right
lambda Lambda expression Left to Right

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 CHAPTER-4
FLOW OF CONTROL

1. Decision Making and branching (Conditional Statement)

2. Looping or Iteration

3. Jumping statements

4.1 DECISION MAKING & BRANCHING

Decision making is about deciding the order of execution of statements based on certain
conditions. Decision structures evaluate multiple expressions which produce TRUE or FALSE
as outcome.

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There are three types of conditions in python:
1. if statement
2. if-else statement
3. elif statement

1. if statement: It is a simple if statement. When condition is true, then code which is

associated with if statement will execute.
Example:
a=40
b=20
if a>b:
print(“a is greater than b”)

2. if-else statement: When the condition is true, then code associated with if statement will
execute, otherwise code associated with else statement will execute.
Example:
a=10
b=20
if a>b:
print(“a is greater”)
else:
print(“b is greater”)

3. elif statement: It is short form of else-if statement. If the previous conditions were not true,
then do this condition". It is also known as nested if statement.
Example:
a=input(“Enter first number”)
b=input("Enter Second Number:")
if a>b:

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 print("a is greater")
elif a==b:
print("both numbers are equal")
else:
print("b is greater")

4.2 LOOPS in PYTHON

Loop: Execute a set of statements repeatedly until a particular condition is satisfied.

There are two types of loops in python:

1. while loop
2. for loop

while
Loops in loop
Python
for loop

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1. while loop: With the while loop we can execute a set of statements as long as a condition is
true. It requires to define an indexing variable.
Example: To print table of number 2
i=2
while i<=20:
print(i)
i+=2

2. for loop : The for loop iterate over a given sequence (it may be list, tuple or string).

Note: The for loop does not require an indexing variable to set beforehand, as the for command
itself allows for this.

primes = [2, 3, 5, 7]
for x in primes:
print(x)

The range( ) function:

it generates a list of numbers, which is generally used to iterate over with for loop.
range( ) function uses three types of parameters, which are:

• start: Starting number of the sequence.

• stop: Generate numbers up to, but not including last number.
• step: Difference between each number in the sequence.

Python use range( ) function in three ways:

a. range(stop)

b. range(start, stop)

c. range(start, stop, step)

Note:

➢ All parameters must be integers.

➢ All parameters can be positive or negative.

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a. range(stop): By default, It starts from 0 and increments by 1 and ends up to stop,
but not including stop value.

Example:

for x in range(4):
print(x)

Output:

0
1
2
3

b. range(start, stop): It starts from the start value and up to stop, but not including
stop value.

Example:

for x in range(2, 6):

print(x)

Output:

2
3
4
5

c. range(start, stop, step): Third parameter specifies to increment or decrement the value by
adding or subtracting the value.

Example:

for x in range(3, 8, 2):

print(x)

Output:

3
5
7

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 Explanation of output: 3 is starting value, 8 is stop value and 2 is step value. First print 3 and
increase it by 2, that is 5, again increase is by 2, that is 7. The output can’t exceed stop-1 value
that is 8 here. So, the output is 3, 5, 8.

Difference between range( ) and xrange( ):

S.
No. range( ) xrange( )

returns the generator object that can be used

1 returns the list of numbers
to display numbers only by looping
The variable storing the range takes more
2 variable storing the range takes less memory
memory
all the operations that can be applied on operations associated to list cannot be
3
the list can be used on it applied on it
4 slow implementation faster implementation

4.3 JUMP STATEMENTS:

There are two jump statements in python:
1. break
2. continue

1. break statement : With the break statement we can stop the loop even if it is true.
Example:
in while loop in for loop
i = 1 languages = ["java", "python", "c++"]
while i < 6: for x in languages:
print(i) if x == "python":
if i == 3: break
break print(x)
i += 1
Output: Output:
1 java
2
3

Note: If the break statement appears in a nested loop, then it will terminate the very loop it is
in i.e. if the break statement is inside the inner loop then it will terminate the inner loop only
and the outer loop will continue as it is.
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2. continue statement : With the continue statement we can stop the current iteration, and
continue with the next iteration.
Example:
in while loop in for loop
i = 0 languages = ["java", "python", "c++"]
while i < 6: for x in languages:
i += 1 if x == "python":
if i == 3: continue
continue print(x)
print(i)

Output: Output:
1 java
2 c++
4
5
6

4.4 Loop else statement:

The else statement of a python loop executes when the loop terminates normally. The else
statement of the loop will not execute when the break statement terminates the loop.
The else clause of a loop appears at the same indentation as that of the loop keyword while or
for.

Syntax:
for loop while loop

for <variable> in <sequence>: while <test condition>:

statement-1 statement-1
statement-2 statement-2
. .
. .
else: else:
statement(s) statement(s)

4.5 Nested Loop :

A loop inside another loop is known as nested loop.

Page 33
Syntax:
for <variable-name> in <sequence>:
for <variable-name> in <sequence>:
statement(s)
statement(s)

Example:

for i in range(1,4):
for j in range(1,i):
print("*", end=" ")
print(" ")

Programs related to Conditional, looping and jumping statements

1. Write a program to check a number whether it is even or odd.
num=int(input("Enter the number: "))
if num%2==0:
print(num, " is even number")
else:
print(num, " is odd number")

2. Write a program in python to check a number whether it is prime or not.

num=int(input("Enter the number: "))
for i in range(2,num):
if num%i==0:
print(num, "is not prime number")
break;
else:
print(num,"is prime number")

Page 34
3. Write a program to check a year whether it is leap year or not.
year=int(input("Enter the year: "))
if year%100==0 and year%400==0:
print("It is a leap year")
elif year%4==0:
print("It is a leap year")
else:
print("It is not leap year")

4. Write a program in python to convert °C to °F and vice versa.

a=int(input("Press 1 for C to F \n Press 2 for F to C \n"))
if a==1:
c=float(input("Enter the temperature in degree celcius: "))
f= (9/5)*c+32
print(c, "Celcius = ",f," Fahrenheit")
elif a==2:
f=float(input("Enter the temperature in Fahrenheit: "))
c= (f-32)*5/9
print(f, "Fahrenheit = ",c," Celcius")
else:
print("You entered wrong choice")

5. Write a program to check a number whether it is palindrome or not.

num=int(input("Enter a number : "))
n=num
res=0
while num>0:
rem=num%10

Page 35
 res=rem+res*10
num=num//10
if res==n:
print("Number is Palindrome")
else:
print("Number is not Palindrome")

6. A number is Armstrong number or not.

num=input("Enter a number : ")
length=len(num)
n=int(num)
num=n
sum=0
while n>0:
rem=n%10
sum=sum+rem**length
n=n//10
if num==sum:
print(num, "is armstrong number")
else:
print(num, "is not armstrong number")

7. To check whether the number is perfect number or not

num=int(input("Enter a number : "))
sum=0
for i in range(1,num):
if(num%i==0):
sum=sum+i

Page 36
 if num==sum:
print(num, "is perfect number")
else:
print(num, "is not perfect number")

8. Write a program to print Fibonacci series.

n=int(input("How many numbers : "))
first=0
second=1
i=3
print(first, second, end=" ")
while i<=n:
third=first+second
print(third, end=" ")
first=second
second=third
i=i+1
9. To print a pattern using nested loops
for i in range(1,5): 1
for j in range(1,i+1): 1 2
print(j," ", end=" ") 1 2 3
print('\n') 1 2 3 4

Page 37
 CHAPTER-5
FUNCTIONS IN PYTHON
5.1 Definition: Functions are the subprograms that perform specific task. Functions are
the
small modules.

5.2 Types of Functions:

There are two types of functions in python:
1. Library Functions (Built in functions)
2. Functions defined in modules
3. User Defined Functions

Built in functions

Functions defined in
Types of functions modules

User defined functions

1. Library Functions: These functions are already built in the python library.

2. Functions defined in modules: These functions defined in particular modules. When

you want to use these functions in program, you have to import the corresponding module
of that function.

3. User Defined Functions: The functions those are defined by the user are called user
defined functions.

1. Library Functions in Python:

These functions are already built in the library of python.
For example: type( ), len( ), input( ) etc.

Page 38
2. Functions defined in modules:
a. Functions of math module:
To work with the functions of math module, we must import math module in program.
import math
S. No. Function Description Example
1 sqrt( ) Returns the square root of a number >>>math.sqrt(49)
7.0
2 ceil( ) Returns the upper integer >>>math.ceil(81.3)
82
3 floor( ) Returns the lower integer >>>math.floor(81.3)
81
4 pow( ) Calculate the power of a number >>>math.pow(2,3)
8.0
5 fabs( ) Returns the absolute value of a number >>>math.fabs(-5.6)
5.6
6 exp( ) Returns the e raised to the power i.e. e3 >>>math.exp(3)
20.085536923187668

b. Function in random module:

random module has a function randint( ).
➢ randint( ) function generates the random integer values including start and end values.
➢ Syntax: randint(start, end)
➢ It has two parameters. Both parameters must have integer values.

Example:
import random
n=random.randint(3,7)

*The value of n will be 3 to 7.

3. USER DEFINED FUNCTIONS:

The syntax to define a function is:
def function-name ( parameters) :
#statement(s)

Page 39
Where:

➢ Keyword def marks the start of function header.

➢ A function name to uniquely identify it. Function naming follows the same rules of
writing identifiers in Python.
➢ Parameters (arguments) through which we pass values to a function. They are optional.
➢ A colon (:) to mark the end of function header.
➢ One or more valid python statements that make up the function body. Statements must
have same indentation level.
➢ An optional return statement to return a value from the function.

Example:

def display(name):

print("Hello " + name + " How are you?")

5.3 Function Parameters:

A functions has two types of parameters:
1. Formal Parameter: Formal parameters are written in the function prototype and function
header of the definition. Formal parameters are local variables which are assigned values from
the arguments when the function is called.
2. Actual Parameter: When a function is called, the values that are passed in the call are
called actual parameters. At the time of the call each actual parameter is assigned to the
corresponding formal parameter in the function definition.
Example :
def ADD(x, y): #Defining a function and x and y are formal parameters
z=x+y
print("Sum = ", z)
a=float(input("Enter first number: " ))
b=float(input("Enter second number: " ))
ADD(a,b) #Calling the function by passing actual parameters
In the above example, x and y are formal parameters. a and b are actual parameters.

Page 40
5.4 Calling the function:
Once we have defined a function, we can call it from another function, program or even the
Python prompt. To call a function we simply type the function name with appropriate
parameters.

Syntax:
function-name(parameter)
Example:
ADD(10,20)

OUTPUT:
Sum = 30.0

How function works?

def functionName(parameter):
… .. …
… .. …
… .. …
… .. …
functionName(parameter)

… .. …
… .. …

The return statement:

The return statement is used to exit a function and go back to the place from where it was
called.
There are two types of functions according to return statement:
a. Function returning some value (non-void function)
b. Function not returning any value (void function)

Page 41
a. Function returning some value (non-void function) :
Syntax:
return expression/value
Example-1: Function returning one value
def my_function(x):
return 5 * x

Example-2 Function returning multiple values:

def sum(a,b,c):
return a+5, b+4, c+7
S=sum(2,3,4) # S will store the returned values as a tuple
print(S)

OUTPUT:
(7, 7, 11)

Example-3: Storing the returned values separately:

def sum(a,b,c):
return a+5, b+4, c+7
s1, s2, s3=sum(2, 3, 4) # storing the values separately
print(s1, s2, s3)

OUTPUT:
7 7 11

b. Function not returning any value (void function) : The function that performs some
operationsbut does not return any value, called void function.
def message():
print("Hello")

m=message()
print(m)

Page 42
 OUTPUT:
Hello
None

5.5 Scope and Lifetime of variables:

Scope of a variable is the portion of a program where the variable is recognized. Parameters
and variables defined inside a function is not visible from outside. Hence, they have a local
scope.

There are two types of scope for variables:

1. Local Scope

2. Global Scope

1. Local Scope: Variable used inside the function. It can not be accessed outside the function.
In this scope, The lifetime of variables inside a function is as long as the function executes.
They are destroyed once we return from the function. Hence, a function does not remember the
value of a variable from its previous calls.

2. Global Scope: Variable can be accessed outside the function. In this scope, Lifetime of a
variable is the period throughout which the variable exits in the memory.

Example:

def my_func():
x = 10
print("Value inside function:",x)

x = 20
my_func()
print("Value outside function:",x)

OUTPUT:

Value inside function: 10

Value outside function: 20

Page 43
Here, we can see that the value of x is 20 initially. Even though the function my_func()changed
the value of x to 10, it did not affect the value outside the function.

This is because the variable x inside the function is different (local to the function) from the
one outside. Although they have same names, they are two different variables with different
scope.

On the other hand, variables outside of the function are visible from inside. They have a global
scope.

We can read these values from inside the function but cannot change (write) them. In order to
modify the value of variables outside the function, they must be declared as global variables
using the keyword global.

Page 44
 CHAPTER-6
STRINGIN PYTHON

6.1 Introduction:
Definition: Sequence of characters enclosed in single, double or triple quotation marks.
Basics of String:
➢ Strings are immutable in python. It means it is unchangeable. At the same memory
address, the new value cannot be stored.

➢ Each character has its index or can be accessed using its index.

➢ String in python has two-way index for each location. (0, 1, 2, ……. In the forward
direction and -1, -2, -3, ........... in the backward direction.)
Example:
0 1 2 3 4 5 6 7
k e n d r i y a
-8 -7 -6 -5 -4 -3 -2 -1

➢ The index of string in forward direction starts from 0 and in backward direction starts
from -1.
➢ The size of string is total number of characters present in the string. (If there are n
characters in the string, then last index in forward direction would be n-1 and last index
in backward direction would be –n.)

➢ String are stored each character in contiguous location.

➢ The character assignment is not supported in string because strings are immutable.
Example :
str = “kendriya”
str[2] = ‘y’ # it is invalid. Individual letter assignment not allowed in python

6.2 Traversing a String:

Access the elements of string, one character at a time.
Page 45
str = “kendriya”
for ch in str :
print(ch, end= ‘ ‘)

Page 46
 Output:
kendriya

6.3 String Operators:

a. Basic Operators (+, *)
b. Membership Operators ( in, not in)
c. Comparison Operators (==, !=, <, <=, >, >=)

a. Basic Operators: There are two basic operators of strings:

i. String concatenation Operator (+)
ii. String repetition Operator (*)

i. String concatenation Operator: The + operator creates a new string by joining the two
operand strings.
Example:
>>>”Hello”+”Python”
‘HelloPython’
>>>’2’+’7’
’27’
>>>”Python”+”3.0”
‘Python3.0’

Note: You cannot concate numbers and strings as operands with + operator.
Example:
>>>7+’4’ # unsupported operand type(s) for +: 'int' and 'str'
It is invalid and generates an error.

Page 47
ii. String repetition Operator: It is also known as String replication operator. It requires
two types of operands- a string and an integer number.
Example:
>>>”you” * 3
‘youyouyou’
>>>3*”you”
‘youyouyou’

Note:You cannot have strings as n=both the operands with * operator.

Example:
>>>”you” * “you” # can't multiply sequence by non-int of type 'str'
It is invalid and generates an error.

b. Membership Operators:
in – Returns True if a character or a substring exists in the given string; otherwise False
not in - Returns True if a character or a substring does not exist in the given string; otherwise False

Example:
>>> "ken" in "Kendriya Vidyalaya"
False
>>> "Ken" in "Kendriya Vidyalaya"
True
>>>"ya V" in "Kendriya Vidyalaya"
True
>>>"8765" not in "9876543"
False

c. Comparison Operators: These operators compare two strings character by character

according to their ASCII value.

Page 48
 Characters ASCII (Ordinal) Value

‘0’ to ‘9’ 48 to 57

‘A’ to ‘Z’ 65 to 90

‘a’ to ‘z’ 97 to 122

Example:
>>> 'abc'>'abcD'
False
>>> 'ABC'<'abc'
True
>>> 'abcd'>'aBcD'
True
>>> 'aBcD'<='abCd'
True

6.4 Finding the Ordinal or Unicode value of a character:

Function Description
ord(<character>) Returns ordinal value of a character

chr(<value>) Returns the corresponding character

Example:
>>> ord('b')
98
>>> chr(65)
'A'

Page 49
Program: Write a program to display ASCII code of a character and vice versa.
var=True
while var:
choice=int(input("Press-1 to find the ordinal value \n Press-2 to find a character of a value\n"))
if choice==1:
ch=input("Enter a character : ")
print(ord(ch))
elif choice==2:
val=int(input("Enter an integer value: "))
print(chr(val))
else:
print("You entered wrong choice")

print("Do you want to continue? Y/N")

option=input()
if option=='y' or option=='Y':
var=True
else:
var=False

6.5 Slice operator with Strings:

The slice operator slices a string using a range of indices.
Syntax:
string-name[start:end]
where start and end are integer indices. It returns a string from the index start to end-1.
0 1 2 3 4 5 6 7 8 9 10 11 12 13
d a t a s t r u c t u r e
-14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1

Page 50
Example:
>>> str="data structure"
>>> str[0:14]
'data structure'
>>> str[0:6]
'data s'
>>> str[2:7]
'ta st'
>>> str[-13:-6]
'ata str'
>>> str[-5:-11]
'' #returns empty string
>>> str[:14] # Missing index before colon is considered as 0.
'data structure'
>>> str[0:] # Missing index after colon is considered as 14. (length of string)
'data structure'
>>> str[7:]
'ructure'
>>> str[4:]+str[:4]
' structuredata'
>>> str[:4]+str[4:] #for any index str[:n]+str[n:] returns original string
'data structure'
>>> str[8:]+str[:8]
'ucturedata str'
>>> str[8:], str[:8]
('ucture', 'data str')
Slice operator with step index:
Slice operator with strings may have third index. Which is known as step. It is optional.

Page 51
Syntax:
string-name[start:end:step]
Example:
>>> str="data structure"
>>> str[2:9:2]
't tu'
>>> str[-11:-3:3]
'atc'
>>> str[: : -1] # reverses a string
'erutcurts atad'

Interesting Fact: Index out of bounds causes error with strings but slicing a string outside the
index does not cause an error.
Example:
>>>str[14]
IndexError: string index out of range
>>> str[14:20] # both indices are outside the bounds
' ' # returns empty string
>>> str[10:16]
'ture'

Reason: When you use an index, you are accessing a particular character of a string, thus the
index must be valid and out of bounds index causes an error as there is no character to return
from the given index.
But slicing always returns a substring or empty string, which is valid sequence.

6.6 Built-in functions of string:

Example:
str=”data structure”

Page 52
s1= “hello365”
s2= “python”
s3 = ‘4567’
s4 = ‘ ‘
s5= ‘comp34%@’
S. No. Function Description Example
1 len( ) Returns the length of a string >>>print(len(str))
14
2 capitalize( ) Returns a string with its first character >>> str.capitalize()
capitalized. 'Data structure'
3 find(sub,start,end) Returns the lowest index in the string where the >>> str.find("ruct",5,13)
substring sub is found within the slice range. 7
Returns -1 if sub is not found. >>> str.find("ruct",8,13)
-1
4 isalnum( ) Returns True if the characters in the string are >>>s1.isalnum( )
alphabets or numbers. False otherwise True
>>>s2.isalnum( )
True
>>>s3.isalnum( )
True
>>>s4.isalnum( )
False
>>>s5.isalnum( )
False
5 isalpha( ) Returns True if all characters in the string are >>>s1.isalpha( )
alphabetic. False otherwise. False
>>>s2.isalpha( )
True
>>>s3.isalpha( )
False
>>>s4.isalpha( )
False
>>>s5.isalpha( )
False
6 isdigit( ) Returns True if all the characters in the string are >>>s1.isdigit( )
digits. False otherwise. False
>>>s2.isdigit( )
False
>>>s3.isdigit( )
True
>>>s4.isdigit( )
False
>>>s5.isdigit( )
False
7 islower( ) Returns True if all the characters in the string are >>> s1.islower()
lowercase. False otherwise. True
>>> s2.islower()

Page 53
 True
>>> s3.islower()
False
>>> s4.islower()
False
>>> s5.islower()
True
8 isupper( ) Returns True if all the characters in the string are >>> s1.isupper()
uppercase. False otherwise. False
>>> s2.isupper()
False
>>> s3.isupper()
False
>>> s4.isupper()
False
>>> s5.isupper()
False
9 isspace( ) Returns True if there are only whitespace >>> " ".isspace()
characters in the string. False otherwise. True
>>> "".isspace()
False
10 lower( ) Converts a string in lowercase characters. >>> "HeLlo".lower()
'hello'
11 upper( ) Converts a string in uppercase characters. >>> "hello".upper()
'HELLO'
12 lstrip( ) Returns a string after removing the leading >>> str="data structure"
characters. (Left side). >>> str.lstrip('dat')
if used without any argument, it removes the ' structure'
leading whitespaces. >>> str.lstrip('data')
' structure'
>>> str.lstrip('at')
'data structure'
>>> str.lstrip('adt')
' structure'
>>> str.lstrip('tad')
' structure'
13 rstrip( ) Returns a string after removing the trailing >>> str.rstrip('eur')
characters. (Right side). 'data struct'
if used without any argument, it removes the >>> str.rstrip('rut')
trailing whitespaces. 'data structure'
>>> str.rstrip('tucers')
'data '
14 split( ) breaks a string into words and creates a list out of it >>> str="Data Structure"
>>> str.split( )
['Data', 'Structure']

Page 54
Programs related to Strings:
1. Write a program that takes a string with multiple words and then capitalize the first
letter of each word and forms a new string out of it.
Solution:
s1=input("Enter a string : ")
length=len(s1)
a=0
end=length
s2="" #empty string
while a<length:
if a==0:
s2=s2+s1[0].upper()
a+=1
elif (s1[a]==' 'and s1[a+1]!=''):
s2=s2+s1[a]
s2=s2+s1[a+1].upper()
a+=2
else:
s2=s2+s1[a]
a+=1
print("Original string : ", s1)
print("Capitalized wrds string: ", s2)

2. Write a program that reads a string and checks whether it is a palindrome string or
not.
str=input("Enter a string : ")
n=len(str)
mid=n//2
rev=-1

Page 55
 for i in range(mid):
if str[i]==str[rev]:
i=i+1
rev=rev-1
else:
print("String is not palindrome")
break
else:
print("String is palindrome")

3. Write a program to convert lowercase alphabet into uppercase and vice versa.
choice=int(input("Press-1 to convert in lowercase\n Press-2 to convert in uppercase\n"))
str=input("Enter a string: ")
if choice==1:
s1=str.lower()
print(s1)
elif choice==2:
s1=str.upper()
print(s1)
else:
print("Invalid choice entered")

Page 56
 CHAPTER-7
LIST IN PYTHON

7.1 Introduction:

▪ List is a collection of elements which is ordered and changeable (mutable).

▪ Allows duplicate values.
▪ A list contains items separated by commas and enclosed within square brackets ([ ]).
▪ All items belonging to a list can be of different data type.
▪ The values stored in a list can be accessed using the slice operator ([ ] and [:]) with
indexes starting at 0 in the beginning of the list.

Difference between list and string:

List String
Mutable Immutable
Element can be assigned at specified Element/character cannot be
index assigned at specified index.
Example: Example:

>>>L=[7,4,8,9] >>>str= “python”

>>>L[2]=6 #valid >>>str[2]= ‘p’ #error

7.2 Creating a list:

To create a list enclose the elements of the list within square brackets and separate the
elements by commas.

Syntax:

list-name= [item-1, item-2,..........., item-n]

Example:

mylist = ["apple", "banana", "cherry"] # a list with three items

L=[] # an empty list

7.2.1 Creating a list using list( ) Constructor:

o It is also possible to use the list( ) constructor to make a list.

Page 57
 mylist = list(("apple", "banana", "cherry")) #note the double round-brackets
print(mylist)

L=list( ) # creating empty list

7.2.2 Nested Lists:

>>> L=[23,'w',78.2, [2,4,7],[8,16]]

>>> L

[23, 'w', 78.2, [2, 4, 7], [8, 16]]

7.2.3 Creating a list by taking input from the user:

>>> List=list(input("enter the elements: "))

enter the elements: hello python

>>> List

['h', 'e', 'l', 'l', 'o', ' ', 'p', 'y', 't', 'h', 'o', 'n']

>>> L1=list(input("enter the elements: "))

enter the elements: 678546

>>> L1

['6', '7', '8', '5', '4', '6'] # it treats elements as the characters though we entered digits

To overcome the above problem, we can use eval( ) method, which identifies the
data type and evaluate them automatically.

>>> L1=eval(input("enter the elements: "))

enter the elements: 654786

>>> L1

654786 # it is an integer, not a list

>>> L2=eval(input("enter the elements: "))

Page 58
 enter the elements: [6,7,8,5,4,3] # for list, you must enter the [ ] bracket

>>> L2

[6, 7, 8, 5, 4, 3]

Note: With eval( ) method, If you enter elements without square bracket[ ], it will be
considered as a tuple.

>>> L1=eval(input("enter the elements: "))

enter the elements: 7,65,89,6,3,4

>>> L1

(7, 65, 89, 6, 3, 4) #tuple

7.3 Accessing lists:

➢ The values stored in a list can be accessed using the slice operator ([ ] and [:]) with
indexes.
➢ List-name[start:end] will give you elements between indices start to end-1.
➢ The first item in the list has the index zero (0).

Example:
>>> number=[12,56,87,45,23,97,56,27]

Forward Index
0 1 2 3 4 5 6 7
12 56 87 45 23 97 56 27
-8 -7 -6 -5 -4 -3 -2 -1
Backward Index

>>> number[2]
87
>>> number[-1]
27
>>> number[-8]
12
>>> number[8]
IndexError: list index out of range
>>> number[5]=55 #Assigning a value at the specified index
Page 59
>>> number
[12, 56, 87, 45, 23, 55, 56, 27]

7.4 Traversing a LIST:

Traversing means accessing and processing each element.

Method-1:

>>> day=list(input("Enter elements :"))

Enter elements : sunday
>>> for d in day:
print(d)

Output:
s
u
n
d
a
y

Method-2
>>> day=list(input("Enter elements :"))
Enter elements : wednesday
>>> for i in range(len(day)):
print(day[i])

Output:
w
e
d
n
e
s
d
a
y

7.5 List Operators:

➢ Joining operator +
➢ Repetition operator *
➢ Slice operator [:]
➢ Comparison Operator <, <=, >, >=, ==, !=

Page 60
• Joining Operator: It joins two or more lists.

Example:

>>> L1=['a',56,7.8]

>>> L2=['b','&',6]

>>> L3=[67,'f','p']

>>> L1+L2+L3

['a', 56, 7.8, 'b', '&', 6, 67, 'f', 'p']

• Repetition Operator: It replicates a list specified number of times.

Example:

>>> L1*3

['a', 56, 7.8, 'a', 56, 7.8, 'a', 56, 7.8]

>>> 3*L1

['a', 56, 7.8, 'a', 56, 7.8, 'a', 56, 7.8]

• Slice Operator:

List-name[start:end] will give you elements between indices start to end-1.

>>> number=[12,56,87,45,23,97,56,27]

>>> number[2:-2]

[87, 45, 23, 97]

>>> number[4:20]

[23, 97, 56, 27]

>>> number[-1:-6]

[]

>>> number[-6:-1]

[87, 45, 23, 97, 56]

Page 61
 >>> number[0:len(number)]

[12, 56, 87, 45, 23, 97, 56, 27]

List-name[start:end:step] will give you elements between indices start to end-1 with
skipping elements as per the value of step.

>>> number[1:6:2]

[56, 45, 97]

>>> number[: : -1]

[27, 56, 97, 23, 45, 87, 56, 12] #reverses the list

List modification using slice operator:

>>> number=[12,56,87,45,23,97,56,27]

>>> number[2:4]=["hello","python"]

>>> number

[12, 56, 'hello', 'python', 23, 97, 56, 27]

>>> number[2:4]=["computer"]

>>> number

[12, 56, 'computer', 23, 97, 56, 27]

Note: The values being assigned must be a sequence (list, tuple or string)

Example:

>>> number=[12,56,87,45,23,97,56,27]

>>> number=[12,56,87,45,23,97,56,27]

>>> number[2:3]=78 # 78 is a number, not a sequence

TypeError: can only assign an iterable

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• Comparison Operators:

o Compares two lists

o Python internally compares individual elements of lists in lexicographical
order.
o It compares the each corresponding element must compare equal and two
sequences must be of the same type.
o For non-equal comparison as soon as it gets a result in terms of True/False,
from corresponding elements’ comparison. If Corresponding elements are
equal, it goes to the next element and so on, until it finds elements that differ.

Example:

>>>L1, L2 = [7, 6, 9], [7, 6, 9]

>>>L3 = [7, [6, 9] ]

For Equal Comparison:

Comparison Result Reason

>>>L1==L2 True Corresponding elements have same value and same
type
>>>L1==L3 False Corresponding values are not same

For Non-equal comparison:

Comparison Result Reason

>>> L1>L2 False All elements are equal
>>> L2>L3 TypeError: '>' not in L2, element at the index 1 is int type
supported between and in L3 element at the index 1 is list
instances of 'int' and
type
'list'
>>>[3,4,7,8]<[5,1] True 3<5 is True
>>>[3,4,7,8]<[3,4,9,2] True First two elements are same so move
to next element and 7<9 is True

>>>[3,4,7,8]<[3,4,9,11] True 7<9 is True

>>>[3,4,7,8]<[3,4,7,5] False 8<5 is False

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List Methods:

Consider a list:

company=["IBM","HCL","Wipro"]

S. Function
No. Description Example
Name
1 append( ) To add element to the list >>> company.append("Google")
at the end. >>> company
Syntax: ['IBM', 'HCL', 'Wipro', 'Google']
list-name.append (element)
Error:
>>>company.append("infosys","microsoft") # takes exactly one element
TypeError: append() takes exactly one argument (2 given)

2 extend( ) Add a list, to the end of >>>company=["IBM","HCL","Wipro"]

the current list. >>> desktop=["dell","HP"]
Syntax: >>> company.extend(desktop)
list-name.extend(list) >>> company
['IBM', 'HCL', 'Wipro', 'dell', 'HP']
Error:
>>>company.extend("dell","HP") #takes only a list as argument
TypeError: extend() takes exactly one argument (2 given)

3. len( ) Find the length of the list. >>>company=["IBM","HCL","Wipro"]

Syntax: >>> len(company)
len(list-name) 3
>>> L=[3,6,[5,4]]
>>> len(L)
3

4 index( ) Returns the index of the >>> company = ["IBM", "HCL", "Wipro",
first element with the "HCL","Wipro"]
specified value. >>> company.index("Wipro")
Syntax: 2
list-name.index(element)
Error:
>>> company.index("WIPRO") # Python is case-sensitive language
ValueError: 'WIPRO' is not in list

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>>> company.index(2) # Write the element, not index
ValueError: 2 is not in list
5 insert( ) Adds an element at the >>>company=["IBM","HCL","Wipro"]
specified position. >>> company.insert(2,"Apple")
>>> company
Syntax: ['IBM', 'HCL', 'Apple', 'Wipro']
list.insert(index, element)
>>> company.insert(16,"Microsoft")
>>> company
['IBM', 'HCL', 'Apple', 'Wipro',
'Microsoft']

>>> company.insert(-16,"TCS")
>>> company
['TCS', 'IBM', 'HCL', 'Apple', 'Wipro',
'Microsoft']

6 count( ) Return the number of >>> company = ["IBM", "HCL",

times the value appears. "Wipro", "HCL","Wipro"]
Syntax: >>> company.count("HCL")
list-name.count(element) 2
>>> company.count("TCS")
0

7 remove( ) To remove an element >>> company = ["IBM", "HCL",

from the list. "Wipro", "HCL","Wipro"]
Syntax: >>> company.remove("Wipro")
list-name.remove(element) >>> company
['IBM', 'HCL', 'HCL', 'Wipro']
Error:
>>> company.remove("Yahoo")
ValueError: list.remove(x): x not in list
8 clear( ) Removes all the elements >>> company=["IBM","HCL", "Wipro"]
from list.
Syntax: >>> company.clear( )
list-name.clear( )
>>> company

[]

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 9 pop( ) Removes the element at >>>company=["IBM","HCL", "Wipro"]
the specified position and >>> company.pop(1)
returns the deleted 'HCL'
element. >>> company
Syntax: ['IBM', 'Wipro']
list-name.pop(index)
>>> company.pop( )
The index argument is
'Wipro'
optional. If no index is
specified, pop( ) removes and
returns the last item in the list.

Error:
>>>L=[ ]
>>>L.pop( )
IndexError: pop from empty list
10 copy( ) Returns a copy of the list. >>>company=["IBM","HCL", "Wipro"]
>>> L=company.copy( )
Syntax: >>> L
list-name.copy( ) ['IBM', 'HCL', 'Wipro']
11 reverse( ) Reverses the order of the >>>company=["IBM","HCL", "Wipro"]
list. >>> company.reverse()
Syntax: >>> company
list-name.reverse( ) ['Wipro', 'HCL', 'IBM']

Takes no argument,
returns no list.
12. sort( ) Sorts the list. By default >>>company=["IBM","HCL", "Wipro"]
in ascending order. >>>company.sort( )
>>> company
Syntax: ['HCL', 'IBM', 'Wipro']
list-name.sort( )
To sort a list in descending order:

>>>company=["IBM","HCL", "Wipro"]
>>> company.sort(reverse=True)
>>> company
['Wipro', 'IBM', 'HCL']

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Deleting the elements from the list using del statement:

Syntax:

del list-name[index] # to remove element at specified index

del list-name[start:end] # to remove elements in list slice

Example:
>>> L=[10,20,30,40,50]

>>> del L[2] # delete the element at the index 2

>>> L

[10, 20, 40, 50]

>>> L= [10,20,30,40,50]

>>> del L[1:3] # deletes elements of list from index 1 to 2.

>>> L

[10, 40, 50]

>>> del L # deletes all elements and the list object too.

>>> L

NameError: name 'L' is not defined

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 Difference between del, remove( ), pop( ), clear( ):

S.
del remove( ) pop( ) clear( )
No.

1 Statement Function Function Function

Deletes a single element Removes the first Removes an

Removes all the
2 or a list slice or complete matching item individual item and
elements from list.
list. from the list. returns it.
Removes all elements Removes all
3 and deletes list object elements but list
too. object still exists.

Difference between append( ), extend( ) and insert( ) :

S.
append( ) extend( ) insert( )
No.
Adds an element at the
Adds single element in the end Add a list in the end of
1 specified position.
of the list. the another list
(Anywhere in the list)
Takes one list as Takes two arguments,
2 Takes one element as argument
argument position and element.
The length of the list
The length of the list will The length of the list
3 will increase by the
increase by 1. will increase by 1.
length of inserted list.

ACCESSING ELEMENTS OF NESTED LISTS:

Example:
>>> L=["Python", "is", "a", ["modern", "programming"], "language", "that", "we", "use"]
>>> L[0][0]
'P'
>>> L[3][0][2]
'd'

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>>> L[3:4][0]
['modern', 'programming']
>>> L[3:4][0][1]
'programming'
>>> L[3:4][0][1][3]
'g'
>>> L[0:9][0]
'Python'
>>> L[0:9][0][3]
'h'
>>> L[3:4][1]
IndexError: list index out of range

Programs related to lists in python:

Program-1 Write a program to find the minimum and maximum number in a list.

L=eval(input("Enter the elements: "))

n=len(L)
min=L[0]
max=L[0]
for i in range(n):
if min>L[i]:
min=L[i]
if max<L[i]:
max=L[i]

print("The minimum number in the list is : ", min)

print("The maximum number in the list is : ", max)

Page 69
Program-2 Find the second largest number in a list.
L=eval(input("Enter the elements: "))
n=len(L)
max=second=L[0]
for i in range(n):
if max<L[i]>second:
max=L[i]
seond=max

print("The second largest number in the list is : ", second)

Program-3: Program to search an element in a list. (Linear Search).

L=eval(input("Enter the elements: "))

n=len(L)
item=eval(input("Enter the element that you want to search : "))
for i in range(n):
if L[i]==item:
print("Element found at the position :", i+1)
break
else:
print("Element not Found")

Output:
Enter the elements: 56,78,98,23,11,77,44,23,65
Enter the element that you want to search : 23
Element found at the position : 4

Page 70
 CHAPTER-8
TUPLE IN PYTHON

8.1 INTRODUCTION:

▪ Tuple is a collection of elements which is ordered and unchangeable (Immutable).

Immutable means you cannot change elements of a tuple in place.
▪ Allows duplicate members.
▪ Consists the values of any type, separated by comma.
▪ Tuples are enclosed within parentheses ( ).
▪ Cannot remove the element from a tuple.

8.2 Creating Tuple:

Syntax:

tuple-name = ( ) # empty tuple

tuple-name = (value-1, value-2, ............, value-n)

Example:

>>> T=(23, 7.8, 64.6, 'h', 'say')

>>> T

(23, 7.8, 64.6, 'h', 'say')

8.2.1 Creating a tuple with single element:

>>> T=(3) #With a single element without comma, it is a value only, not a tuple

>>> T

>>> T= (3, ) # to construct a tuple, add a comma after the single element

>>> T

(3,)

Page 71
>>> T1=3, # It also creates a tuple with single element

>>> T1

(3,)

8.2.2 Creating a tuple using tuple( ) constructor:

o It is also possible to use the tuple( ) constructor to create a tuple.

>>>T=tuple( ) # empty tuple

>>> T=tuple((45,3.9, 'k',22)) #note the double round-brackets

>>> T
(45, 3.9, 'k', 22)

>>> T2=tuple('hello') # for single round-bracket, the argument must be of sequence type
>>> T2
('h', 'e', 'l', 'l', 'o')

>>> T3=('hello','python')
>>> T3
('hello', 'python')

8.2.3 Nested Tuples:

>>> T=(5,10,(4,8))

>>> T

(5, 10, (4, 8))

8.2.4 Creating a tuple by taking input from the user:

>>> T=tuple(input("enter the elements: "))

enter the elements: hello python

>>> T

Page 72
('h', 'e', 'l', 'l', 'o', ' ', 'p', 'y', 't', 'h', 'o', 'n')

>>> T1=tuple(input("enter the elements: "))

enter the elements: 45678

>>> T1

('4', '5', '6', '7', '8') # it treats elements as the characters though we entered digits

To overcome the above problem, we can use eval( ) method, which identifies the
data type and evaluate them automatically.

>>> T1=eval(input("enter the elements: "))

enter the elements: 56789

>>> T1

56789 # it is not a list, it is an integer value

>>> type(T1)

<class 'int'>

>>> T2=eval(input("enter the elements: "))

enter the elements: (1,2,3,4,5) # Parenthesis is optional

>>> T2

(1, 2, 3, 4, 5)

>>> T3=eval(input("enter the elements: "))

enter the elements: 6, 7, 3, 23, [45,11] # list as an element of tuple

>>> T3

(6, 7, 3, 23, [45, 11])

Page 73
8.3 Accessing Tuples:

Tuples are very much similar to lists. Like lists, tuple elements are also indexed.
Forward indexing as 0,1,2,3,4……… and backward indexing as -1,-2,-3,-4,………

➢ The values stored in a tuple can be accessed using the slice operator ([ ] and [:]) with
indexes.
➢ tuple-name[start:end] will give you elements between indices start to end-1.
➢ The first item in the tuple has the index zero (0).

Example:

>>> alpha=('q','w','e','r','t','y')

Forward Index
0 1 2 3 4 5
q w e r t y
-6 -5 -4 -3 -2 -1
Backward Index

>>> alpha[5]
'y'
>>> alpha[-4]
'e'
>>> alpha[46]
IndexError: tuple index out of range
>>> alpha[2]='b' #can’t change value in tuple, the value will remain unchanged
TypeError: 'tuple' object does not support item assignment

8.3.1 Difference between List and Tuple:

S. No. List Tuple

1 Ordered and changeable (Mutable) Ordered but unchangeable (Immutable)

2 Lists are enclosed in brackets. [] Tuples are enclosed in parentheses. ( )

3 Element can be removed. Element can’t be removed.

Page 74
 8.4 Traversing a Tuple:

Syntax:

for <variable> in tuple-name:

statement

Example:

Method-1

>>> alpha=('q','w','e','r','t','y')
>>> for i in alpha:
print(i)

Output:
q
w
e
r
t
y

Method-2
>>> for i in range(0, len(alpha)):
print(alpha[i])

Output:
q
w
e
r
t
y

8.5 Tuple Operations:

➢ Joining operator +
➢ Repetition operator *
➢ Slice operator [:]
➢ Comparison Operator <, <=, >, >=, ==, !=

Page 75
• Joining Operator: It joins two or more tuples.

Example:

>>> T1 = (25,50,75)
>>> T2 = (5,10,15)
>>> T1+T2
(25, 50, 75, 5, 10, 15)

>>> T1 + (34)
TypeError: can only concatenate tuple (not "int") to tuple

>>> T1 + (34, )

(25, 50, 75, 34)

• Repetition Operator: It replicates a tuple, specified number of times.

Example:

>>> T1*2

(25, 50, 75, 25, 50, 75)

>>> T2=(10,20,30,40)

>>> T2[2:4]*3

(30, 40, 30, 40, 30, 40)

• Slice Operator:

tuple-name[start:end] will give you elements between indices start to end-1.

>>>alpha=('q','w','e','r','t','y')

>>> alpha[1:-3]

('w', 'e')

>>> alpha[3:65]

('r', 't', 'y')

>>> alpha[-1:-5]

Page 76
 ()

>>> alpha[-5:-1]

('w', 'e', 'r', 't')

List-name[start:end:step] will give you elements between indices start to end-1 with
skipping elements as per the value of step.

>>> alpha[1:5:2]

('w', 'r')

>>> alpha[ : : -1]

('y', 't', 'r', 'e', 'w', 'q') #reverses the tuple

• Comparison Operators:

o Compare two tuples

o Python internally compares individual elements of tuples in lexicographical
order.
o It compares the each corresponding element must compare equal and two
sequences must be of the same type.
o For non-equal comparison as soon as it gets a result in terms of True/False,
from corresponding elements’ comparison. If Corresponding elements are
equal, it goes to the next element and so on, until it finds elements that differ.

Example:

>>> T1 = (9, 16, 7)

>>> T2 = (9, 16, 7)
>>> T3 = ('9','16','7')
>>> T1 = = T2
True
>>> T1==T3
False
>>> T4 = (9.0, 16.0, 7.0)
>>> T1==T4
True
>>> T1<T2

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 False
>>> T1<=T2
True

8.6 Tuple Methods:

Consider a tuple:

subject=("Hindi","English","Maths","Physics")

S. Function
No. Description Example
Name
1 len( ) Find the length of a tuple. >>>subject=("Hindi","English","Maths","Physics”)
Syntax: >>> len(subject)
len (tuple-name) 4
2 max( ) Returns the largest value >>> max(subject)
from a tuple. 'Physics'
Syntax:
max(tuple-name)
Error: If the tuple contains values of different data types, then it will give an error
because mixed data type comparison is not possible.

>>> subject = (15, "English", "Maths", "Physics", 48.2)

>>> max(subject)
TypeError: '>' not supported between instances of 'str' and 'int'

3. min( ) Returns the smallest >>>subject=("Hindi","English","Maths","Physics")

value from a tuple. >>> min(subject)
Syntax:
min(tuple-name) 'English'
Error: If the tuple contains values of different data types, then it will give an error
because mixed data type comparison is not possible.

>>> subject = (15, "English", "Maths", "Physics", 48.2)

>>> min(subject)
TypeError: '>' not supported between instances of 'str' and 'int'

4 index( ) Returns the index of the >>>subject=("Hindi","English","Maths","Physics")

first element with the

specified value.
Syntax:

Page 78
 tuple- >>> subject.index("Maths")
name.index(element)
2
5 count( ) Return the number of >>> subject.count("English")
times the value appears.
Syntax: 1
tuple-
name.count(element)

8.7 Tuple Packing and Unpacking:

Tuple Packing: Creating a tuple from set of values.

Example:

>>> T=(45,78,22)
>>> T
(45, 78, 22)

Tuple Unpacking : Creating individual values from the elements of tuple.

Example:

>>> a, b, c=T
>>> a
45
>>> b
78
>>> c
22

Note: Tuple unpacking requires that the number of variable on the left side must be equal
to the length of the tuple.

8.8 Delete a tuple:

The del statement is used to delete elements and objects but as you know that tuples are
immutable, which also means that individual element of a tuple cannot be deleted.

Page 79
Example:

>> T=(2,4,6,8,10,12,14)

>>> del T[3]

TypeError: 'tuple' object doesn't support item deletion

But you can delete a complete tuple with del statement as:

Example:

>>> T=(2,4,6,8,10,12,14)

>>> del T

>>> T

NameError: name 'T' is not defined

Page 80
 CHAPTER-9
DICTIONARY INPYTHON

9.1 INTRODUCTION:

▪ Dictionary is a collection of elements which is unordered, changeable and indexed.

▪ Dictionary has keys and values.
▪ Doesn’t have index for values. Keys work as indexes.
▪ Dictionary doesn’t have duplicate member means no duplicate key.
▪ Dictionaries are enclosed by curly braces { }
▪ The key-value pairs are separated by commas ( , )
▪ A dictionary key can be almost any Python type, but are usually numbers or strings.
▪ Values can be assigned and accessed using square brackets [ ].

9.2 CREATING A DICTIONARY:

Syntax:

dictionary-name = {key1:value, key2:value, key3:value, keyn:value}

Example:

>>> marks = { "physics" : 75, "Chemistry" : 78, "Maths" : 81, "CS":78 }

>>> marks

{'physics': 75, 'Chemistry': 78, 'Maths': 81, 'CS': 78}

>>> D = { } #Empty dictionary

>>> D

{ }

>>> marks = { "physics" : 75, "Chemistry" : 78, "Maths" : 81, "CS":78 }

{'Maths': 81, 'Chemistry': 78, 'Physics': 75, 'CS': 78} # there is no guarantee that

# elements in dictionary can be accessed as per specific order.

Page 81
Note: Keys of a dictionary must be of immutable types, such as string, number, tuple.

Example:

>>> D1={[2,3]:"hello"}

TypeError: unhashable type: 'list'

Page 82