Python

In this Page, We are Providing Basics of Python – Operators and Operands. Students can visit for more Detail and Explanation of Python Handwritten Notes Pdf.

Basics of Python – Operators and Operands

Operators and operands

An operator is a symbol (such as +, x, etc.) that represents an operation. An operation is an action or •procedure that produces a new value from one or more input values called operands. There are two types of operators: unary and binary. The unary operator operates only on one operand, such as negation. On the other hand, the binary operator operates on two operands, which include addition, subtraction, multiplication, division, exponentiation operators, etc. Consider an expression 3 + 8, here 3 and 8 are called operands, while V is called operator. The operators can also be categorized into:

• Arithmetic operators.
• Comparison (or Relational) operators.
• Assignment operators.
• Logical operators.
• Bitwise operators.
• Membership operators.
• Identity operators.

Arithematics operators

Table 2-2 enlists the arithmetic operators with a short note on the operators.

The following example illustrates the use of the above-discussed operators.

>>> a=20 
>>> b=45.0
>>> a+b
65.0
>>> a-b
-25.0
>>> a*b
900.0 
>>> b/a 
2.25 
>>> b%a
5.0
>>> a**b
3.5184372088832e+58 
>>> b//a
2.0

Relational operators

A relational operator is an operator that tests some kind of relation between two operands. Tables 2-3 enlist the relational operators with descriptions.

The following example illustrates the use of the above-discussed operators.

>>> a,b=20,40
>>> a==b
False 
>>> a!=b 
True
>>> a<>b 
True 
>>> a>b 
False 
>>> a<b 
True
>>> a>=b 
False 
>>> a<=b 
True

Assignment operators

The assignment operator is an operator which is used to bind or rebind names to values. The augmented assignment is the combination, in a single statement, of a binary operation and an assignment statement. An augmented assignment expression like x+=l can be rewritten as x=x+l. Tables 2-4 enlist the assignment operators with descriptions.

The following example illustrates the use of the above-discussed operators.

>>> a,b=20,40 
>>> c=a+b 
>>> c 
60
>>> a,b=2.0,4.5 
>>>c=a+b
>>> C
6.5
>>> c+=a 
>>> c
8.5
>>> c-=a 
>>> c
6.5
>>> c*=a 
>>> c
13.0
>>> c/=a 
>>> c 
6.5
>>> c%=a 
>>> c 
0.5
>>> c**=a 
>>> c 
0.25
>>> c//=a 
>>> c 
0.0

Bitwise operators

A bitwise operator operates on one or more bit patterns or binary numerals at the level of their individual bits. Tables 2-5 enlist the bitwise operators with descriptions.

The following example illustrates the use of the above-discussed operators.

>>> a,b=60,13 
>>> a&b 
12
>>> a | b
61 
>>> a∧b
49 
>>> ~a
-61 
>>> a< < 2
240 
>>> a>>2
15

In the above example, the binary representation of variables a and b are 00111100 and 00001101, respectively. The above binary operations example is tabulated in Tables 2-6.

Logical operators

Logical operators compare boolean expressions and return a boolean result. Tables 2-6 enlist the logical operators with descriptions.

The following example illustrates the use of the above-discussed operators.

>>> 5>2 and 4<8 
True
>>> 5>2 or 4>8 
True
>>> not (5>2)
False

Membership operators

A membership operator is an operator which tests for membership in a sequence, such as string, list, tuple, etc. Table 2-7 enlists the membership operators.

>>> 5 in [0, 5, 10, 15]
True 
>>> 6 in [0, 5, 10, 15]
False
>>> 5 not in [0, 5, 10, 15]
False 
>>> 6 not in [0, 5, 10, 15]
True

Identity operators

Identity operators compare the memory locations of two objects. Table 2-8 provides a list of identity operators including a small explanation.

The following example illustrates the use of the above-discussed operators.

>>> a=b=3.1
>>> a is b 
True 
>>> id (a)
3 0 9 8 4 5 2 8 
>>> id (b)
30984528 
>>> c,d=3.1,3.1 
>>> c is d 
False 
>>> id (c)
35058472 
>>> id (d)
30984592
>>> c is not d
True 
>>> a is not b
False

Operator precedence

Operator precedence determines how an expression is evaluated. Certain operators have higher precedence than others; for example, the multiplication operator has higher precedence than the addition operator. In the expression x=7+3*2, x is assigned 13, not 20, because operator * has higher precedence than +, so it first multiplies 3*2 and then adds into 7.

Table 2-10 summarizes the operator’s precedence in Python, from lowest precedence to highest precedence (from top to bottom). Operators in the same box have the same precedence.

What is RSS?

RSS stands for Really Simple Syndication or Rich Site Summary. It is a type of web feed that allows users and applications to receive regular updates from a website or blog of their choice. Various website use their RSS feed to publish the frequently updated information like blog entries, news headlines etc, So this is where RSS feeds are mainly used.

So we can use that RSS feed to extract some important information from a particular website. In this article I will be showing how you will extract RSS feeds of any website.

Installing packages

You can install all packages using pip like the example below.

 pip install requests
 pip install bs4

Importing  libraries:

Now our project setup is ready, we can start writing the code.

Within our rssScrapy.py we’ll import the packages we’ve installed using pip.

import requests

from bs4 import BeautifulSoup

The above package will allow us to use the functions given to us by the Requests and BeautifulSoup libraries.

I am going to use the RSS feeds of a news website called Times of India.

Link-"https://timesofindia.indiatimes.com/rssfeeds/1221656.cms"

This is basically an XML file.

So now I am going to show you how this particular xml file will scrape.

import requests
from bs4 import BeautifulSoup
url="https://timesofindia.indiatimes.com/rssfeeds/1221656.cms"
resp=requests.get(url)
soup=BeautifulSoup(resp.content,features="xml")
print(soup.prettify())

We dont nedd all the data having in it.We want news description,title,publish date right.So for this we are going to create a list which contains all the content inside item tags.For this we have used   items=soup.findAll('item') 

You can also check the length of items using this len(items)

So now I am writing whole code for scrapping the news RSS feed-

import requests
from bs4 import BeautifulSoup
url="https://timesofindia.indiatimes.com/rssfeeds/1221656.cms"
resp=requests.get(url)
soup=BeautifulSoup(resp.content,features="xml")
items=soup.findAll('item')
item=items[0]
news_items=[]
for item in items:
    news_item={}
    news_item['title']=item.title.text
    news_item['description']=item.description.text
    news_item['link']=item.link.text
    news_item['guid']=item.guid.text
    news_item['pubDate']=item.pubDate.text
    news_items.append(news_item)
print(news_items[2])

So we can see that I have used item.title.textfor scrapping title because item is parent class and title is child class similarly we do for rest.

Each of the articles available on the RSS feed  containing all information within item tags <item>...</item>.
and follows the below structure-

<item>
    <title>...</title>
    <link>...</link>
    <pubDate>...</pubDate>
    <comments>...</comments>
    <description>...</description>
</item>

We’ll be taking advantage of the consistent item tags to parse our information.

I have also make an empty list news_items which append all in it.

So this is how we can parse particularly news item.

Conclusion:

We have successfully created an RSS feed scraping tool using Python, Requests, and BeautifulSoup. This allows us to parse XML information into a suitable format for us to work with in the future.

In this Page, We are Providing Basics of Python – Variable, Identifier and Literal. Students can visit for more Detail and Explanation of Python Handwritten Notes Pdf.

Basics of Python – Variable, Identifier and Literal

Variable, identifier, and literal

A variable is a storage location that has an associated symbolic name (called “identifier”), which contains some value (can be literal or other data) that can change. An identifier is a name used to identify a variable, function, class, module, or another object. Literal is a notation for constant values of some built-in type. Literal can be string, plain integer, long integer, floating-point number, imaginary number. For e.g., in the expressions

var1=5 
var2= 'Tom'

var1 and var2 are identifiers, while 5 and ‘ Tom’ are integer and string literals, respectively.

Consider a scenario where a variable is referenced by the identifier a and the variable contains a list. If the same variable is referenced by the identifier b as well, and if an element in the list is changed, the change will be reflected in both identifiers of the same variable.

>>> a = [1, 2, 3]
>>> b =a 
>>> b 
[1, 2, 3]
>> a [ 1 ] =10
>>> a
[1, 10, 3]
>>> b
[1, 10, 3]

Now, the above scenario can be modified a bit, where a and b are two different variables.

>>> a= [1,2,3 ]
>>> b=a[:] # Copying data from a to b.
>>> b 
[1, 2, 3]
>>> a [1] =10 
>>> a 
(1, 10, 3]
>>> b
[1, 2, 3]

There are some rules that need to be followed for valid identifier naming:

• The first character of the identifier must be a letter of the alphabet (uppercase or lowercase) or an underscore (‘_’).
• The rest of the identifier name can consist of letters (uppercase or lowercase character), underscores (‘_’), or digits (0-9).
• Identifier names are case-sensitive. For example, myname and myName are not the same.
• Identifiers can be of unlimited length.

In this Page, We are Providing Python Programming – Introduction to Python. Students can visit for more Detail and Explanation of Python Handwritten Notes Pdf.

Python Programming – Introduction to Python

Open-source software

Before stepping into the world of programming using open source tools, one should try to understand the definition of open-source software given by “Open Source Initiative” (abbreviated as OSI). OSI is a non-profit corporation with global scope, formed to educate about and advocate the benefits of open source software, and to build bridges among different constituencies in the open-source community.

Open-source software is a defined as software whose source code is made available under a license that allows modification and re-distribution of the software at will. Sometimes a distinction is made between open source software and free software as given by GNU {http://www.gnu.org/). The detailed distribution terms of open-source software given by OSI are given on the website link: http://opensource. org/.

Python(x,y)

“Python(x,y)” is a free scientific and engineering development software for numerical computations, data analysis, and data visualization based on Python programming language and Spyder interactive development environment, the launcher (current version 2.7.6.0) is shown in figure 1-5. The executable file of Python(x,y) can be downloaded and then installed from the website link: http://code.google.eom/p/pythonxy/. The main features of Python(x,y) are:

• Bundled with scientific-oriented Python libraries and development environment tools.
• Extensive documentation of various Python packages.
• Providing an all-in-one setup program, so that the user can install or uninstall all these packages and features by clicking one button only.

EBNF

A “syntactic metalanguage” is a notation for defining the syntax of a language by the use of a number of rules. A syntactic metalanguage is an important tool of computer science. Since the definition of the programming language “Algol 60”, it has been a custom to define the syntax of a programming language formally. Algol 60 was defined with a notation now known as “Backus-Naur Form” (BNF). This notation has proved a suitable basis for subsequent languages but has frequently been extended or slightly altered.

There are many different notations that are confusing and have prevented the advantages of formal unambiguous definitions from being widely appreciated. “Extended BNF” (abbreviated as EBNF, based on Backus-Naur Form) brings some order to the formal definition of the syntax and is useful not just for the definition of programming languages, but for many other formal definitions. Please refer international standard document (ISO/IEC 14977:1996(E)) for detailed information on EBNF (website link: http://standards.iso.org/ittf/PubliclyAvailobleStandards/).