Python Revision Tour.pptx class 12 python notes

Introduction
Python revision Tour- 1
• Introduction to Python
• Working with Python
• Data types , Operations
• Python Functions, Modules
• Flow of execution
• Statement flow control
Python revision Tour- 2
• Sting in python
• List in python
• Tuple in python
• Dictionary in python

Python used as general purpose, high level programming language. Developed by Guido van Rossum in 1991.
Pros of Python :
• Easy to use – Due to simple syntax rule
• Interpreted language – Code execution & interpretation line by line
• Cross-platform language – It can run on windows, Linux, Macintosh
etc. equally
• Expressive language – Less code to be written as it itself express the
purpose of the code.
• Completeness – Support wide rage of library
• Free & Open Source – Can be downloaded freely and source code
can be modify for improvement

Cons of Python
• Lesser libraries – as compared to other programming languages like
C++, java, .NET
• Slow language – as it is interpreted languages, it executes the
program slowly.
• Weak on Type-binding – It not pin point on use of a single variable for
different data type

Data types in Python
• We know that data types are nothing but the type of data we use to the variable,
method etc.
• We have following data types in Python.
1. Number
2. String
3. Boolean
4. List
5. Tuple
6. Set
7. Dictionary

Number
In Python we use number data type to store numeric value.
• Integer – Whole number without fraction parts ex: 1, 2 etc. Use 32 bits to store
value.
• Long integer – It store larger integer number. Use 32 bits to store value.
• Floating Point – It is a positive or negative real numbers with a
decimal point.
• Complex – Complex numbers are combination of a real and imaginary part.
Complex numbers are in the form of X+Yj, where X is a real part and
Y is imaginary part.
Input : a = complex(5) Output : (5+0j)
print(a)

String
• A string is a sequence of characters. In python we can create string
using single (' ') or double quotes (" ").Both are same in python.
Ex : - Input :
str='computer science’
print('str-', str) # print string
Output :
str- computer science

String Method
Method Description
Capitalize() Returns a copy of string with its first character as capita
Find() Returns the lowest index in the string
Isalnum() Returns true if the character in the string are alphanumeric
Isalpha() Returns true if the character in the string are alphabetic
Isdigit() Returns true if the character in the string are digit
Islower() Returns true if all the cased characters in the string are lowercase
Isupper() Returns true if all the cased characters in the string are uppercase
Title() Returns True if the string is in title case
Swapcase() Returns a copy of the string with uppercase character converted to lowercase and vice
versa
Partition() Splits the string at the first occurrence of argument

String Methods contd..
Method Description
Isspace() Returns true if there are only whitespace character in the string
Count() Returns the number of non-overlapping occurrence of substring in the given string
lstrip Returns a copy of the string with leading characters removed
rstrip Returns a copy of the string with trailing characters removed
Startswith() Returns true if string starts with the argument otherwise return false
Endswith() Returns true if string ends with the argument otherwise return false
Lower() Returns a copy of string converted to lowercase
Upper() Returns a copy of string converted to uppercase
Title() Returns a titlecase version of the string

Boolean
It is used to store two possible values either true or false.
e.g. a=“jnv"
b=str.isupper() # test if string contains upper case
print(b)
Output : False
LIST
List are collections of items and each item has its own index value.

List Methods
Method Description
Index() Returns the index of first matched item from the list
Append() Adds an item to the end of the list
Extend() Adds list at the end
Insert() Insert any item in between the list
Pop() Remove an item from the list
Remove() Remove the first occurrence of the given element
Clear() Remove all the items from the list
Count() Returns the count of the item that passes as argument
Reverse() Reverses the item of the list
Sort() Sort the item of the list, by default in increasing order

Tuples
• Tuples are list of value separated by comma ( , ).
• Tuples are Immutable which means values in the tuple can not
be changed.
• The data type in tuple can be any. Which means we can have
number and string in same tuple.
• Tuple is represented as : ( )
Example: 1) t1 = (1,2,3,4,5,6)
2) t2 = (‘A’ , ‘B’ , ‘C’)
3) t3 = (‘a’ , ‘b’ , 1,2,3,4,5,6)

Tuple Methods
Method Description
Len() Return the length of tuple
Max() Returns the element from the tuple having maximum value
Min() Returns the element from the tuple having minimum value
Index() Returns the index of an existing element of a tuple
Count() Returns the count of the member element / object in a given sequence( list/tuple)
Tuple() Constructor method, create tuple

Dictionary
• It is an unordered collection of items and each item consist of a key and a value.
e.g. dict = {'Subject': 'comp sc', 'class': '11’}
print(dict)
print ("Subject : ", dict['Subject’])
print ("class : ", dict.get('class’))
Output
{'Subject': 'comp sc', 'class': '11’}
Subject : comp sc class : 11
class : 11

Dictionary Method
Method Description
len() Returns length of the dictionary
clear() Remove all method from the dictionary
get() Get the item with the given key
has_keys To check the presence of given key in the dictionary
items() Return all the items of the dictionary
key() Return all the keys in the dictionary
value() Returns all the values from the dictionary in the form of list in no particular order
update() This will merge the key : value pairs from a new dictionary, adding or replacing as
needed
cmp Compare to dictionary based on their elements

List
• A list in python is represented by square bracket [].
• List is assigned to Variable
• The value inside a list can be changed.
example : (1) a = [1,2,3,4,5]
(2) b = [‘A’ , ‘B’ , ‘C’]
(3) c = [1,2, ’A’ , ‘B’ ]

Mutable and Immutable
Mutable data type can change
the value
• Dictionary
• List
Immutable data type can’t be
change value
• String
• Integer
• Tuples
• Booleans
• Floating Point

Arithmetic Operators
Operators are special symbols in Python that carry out arithmetic or logical
computation. The value that the operator operates on is called the operand.
Arithmetic operators Used for mathematical operation
Operator Meaning Example
+ Add two operands x + y +2
- Subtract right operand from the left x - y -2
* Multiply two operands x * y
/ Divide left operand by the right one x / y
% Modulus - remainder of the division x % y
// Floor division - division that results into whole number x // y
** Exponent - left operand raised to the power of right x**y

Comparison operators- Used to compare values
> Greater than - True if x is greater than y x > y
< Less that - True if x is less than y 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 left operand
is greater than or equal to the right x >= y
<= Less than or equal to - True if left operand
is less than or equal to the right x <= y

Logical Operator
and True if both the operands are true x and y
or True if either of the operands is true x or y
not True if operand is false not x

Operators Precedence
Operator~ + - Description
** Exponentiation (raise to the power)
~ + - Complement, unary plus and minus (method names for the last two are +@ and
-@)
* / % // Multiply, divide, modulo and floor division
+ - Addition and subtraction
>> << Right and left bitwise shift
& Bitwise 'AND'
^ | Bitwise exclusive `OR' and regular `OR'
<= < > >= Comparison operators
<> == != Equality operators
= %= /= //= -= += *= **= Assignment operators
is is not Identity operators
in not in Membership operators
not or and Logical operators

Python Function and Module
Python function :
• Function in Python are self
controlled piece of program
which perform a specific task.
• We can use in program whenever
needed by invoking them.
• Categories of python function:
1. Build in unction
2. Function defined in module
3. User defined function.
Python Module :
• It is a python file.
• It’s extension is .py
• Can be re-used in other
programs
• Can depend on other module
• Independent of grouping of code
and data

Statements Flow Control
Control statements are used to control the flow of execution depending
upon the specific condition.
1. Decision making statements
a. if statements
b. if-else statements
c. Nested if-else statement
2. Iteration statements (LOOPS)
a. While Loop
b. For Loop
c. Nested For Loops
3. Jump statements ( Break, continue, Pass )

If Statements
An if statement is a programming conditional statement that, if proved
true, performs a function or displays information.
Input Output
x=1
y=2
if(x==1 and y==2):
print(‘Matched')
Matched

if-else Statements
• If-else statement executes some code if the test expression is true
and some other code if the test expression is false.
Input Output
a=10
if(a < 100):
print(‘less than 100')
else:
print(‘more than equal
100')
less than 100

Nested if-else statement
The nested if...else statement allows you to check for multiple test
expressions and execute different codes for more than two conditions.
Input Output
num = float(input("Enter a
number: "))
if num >= 0:
if num == 0:
print("Zero")
else:
print("Positive number")
else:
print("Negative number")
Enter a number: 4
Positive number

Iteration Statements (Loops)
While Loop
It is used to execute a block of statement as long as a given condition is true. And when the
condition become false, the control will come out of the loop. The condition is checked every time
at the beginning of the loop.
While – else
It is used to execute a block of statement as long as a given condition is true. And when the
condition become false, it execute else part of block of statements and come out of the loop.
Input (While ) Output
x = 1
while (x <= 4):
print(x)
x = x + 1
1
2
3
4
Input (While-else) Output
i = 0
while i < 4:
i += 1
print(i)
else:
print("Breakn")
1
2
3
4
Break

For Loop
• It is used to iterate over items of any sequence, such as a list or a
string.
• e.g.
• for i in range(3,5):
• print(i)
• Output
• 3
• 4

Continue Statement: It returns the control to the beginning of the loop
Break Statement: It brings control out of the loop.
Pass Statement: We use pass statement to write empty loops. Pass is also used for empty control statements,
function and classes.
Input Output
for letter in ‘rajeev':
if letter == 'e' or letter == ‘a':
continue
print( letter)
r
J
v
Input Output
for letter in 'rajeev':
if letter == 'a' or letter == 'j':
break
print('Current Letter :', letter)
Current Letter : a
for letter in 'rajeev':
pass
print('Last Letter :', letter)
Last Letter : v

Python Revision Tour.pptx class 12 python notes

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