13.16. Multiple Choice Questions

Q-1: What protocol can be used to retrieve web pages using python?

• urllib
• urlib is a python library that contains several modules with URLs
• bs4
• bs4 is a python library pulling out data from HTML files.
• HTTP
• HTTP is a network protocol that is used to transmit different documents like HTML.
• GET
• GET is a HTTP request method from a specified resource in a server.

Q-2: What provides two way communication between two different programs in a network.

• socket
• A single socket is a program that can be used to send and receive data in a network.
• port
• A port represents an endpoint on a computer that can connect to different network nodes.
• http
• HTTP is a protocol used for transfer data from a web server.
• protocol
• protocol is a set of rules that determine how data is transmitted over a network.

Q-3: What is a python library that can be used to send and receive data over HTTP?

• http
• http is a protocol and not a python library
• urllib
• urllib can be used to send and receive data over HTTP instead of manually doing it using a webbrowser.
• port
• port is an endpoint for a device to connect with other devices in a network to transmit similar types of data.
• header
• a header is additional information sent and received along with data.

Q-4: What is the process by which search engines retrieve webpages and build a search index called?

• scrape
• Scrape is the act of extraction of webpages
• parse
• Parse is breaking down scraped webpages to useful data
• BeautifulSoup
• BeautifulSoup is a python library for extracting HTML documents
• spider
• spider retrieves a webpage and then all the webpages linked to it to form a search index.

Q-5: What does the following block of code do?

mysock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
mysock.connect(('data.pr4e.org', 80))
cmd = 'GET http://data.pr4e.org/romeo.txt HTTP/1.0\r\n\r\n'.encode()
mysock.send(cmd)

• It sends a request to extract 'romeo.txt' from 'data.pr4e.org'
• this sends a GET request to the webserver over port 80
• It sends the 'romeo.txt' file to 'data.pr4e.org'
• This does not send a file to the webserver.
• It creates a file named 'romeo.txt'
• This does not create a file
• It throws an error because a socket cannot use HTTP.
• sockets can be used to connect with different types of servers using different protocols.

Q-6: What does the following block of code do?

import urllib.request

fhand = urllib.request.urlopen('http://data.pr4e.org/romeo.txt')
for line in fhand:
    print(line.decode().strip())

• It creates a file named 'romeo.txt' in 'data.pr4e.org'
• urllib.request cannot create files in a web server.
• It finds the urls linked to 'data.pr4e.org' and prints it.
• urllib.request is not a spider.
• It opens a file named 'http://data.pr4e.org/romeo.txt' in local storage
• urllib.request does not handle files in local storage
• It prints the contents of 'romeo.txt' after retrieving it from 'data.pr4e.org'
• urllib.request requests the file and then accepts it.

Q-7: What does the following block of code do?

import urllib.request, urllib.parse, urllib.error

img = urllib.request.urlopen('http://data.pr4e.org/cover3.jpg').read()
fhand = open('cover3.jpg', 'wb')
fhand.write(img)
fhand.close()

• It retrieves 'cover3.jpg' and saves it to your computer.
• Running the code does not display any output because it saves the file to your computer.
• It displays the image 'cover3.jpg'.
• It does not output anything on the screen.
• It retrieves the url to download 'cover3.jpg'
• The urllib retrieves the file and parses it.

Q-8: What does the following regex match?

http[s]?://.+?

• Exact match to 'http[s]?://.+?'
• The regex uses wildcard characters and is not an exact match case.
• 'http://' or 'http[s]://' followed by one or more character
• the square brackets denotes a character class with 0 or 1 's'.
• 'http://' or 'https://' followed by one or more characters.
• the '[s]?' means 0 or 1 s and '.+?' means 1 or more characters
• 'https://' followed by one or more characters.
• the regex also accepts 'http://' because '[s]?' means 'http' followed by 0 or 1 's'

Q-9: What does the following block of code do?

url = "https://www.nytimes.com"
html = urllib.request.urlopen(url, context=ctx).read()
soup = BeautifulSoup(html, 'html.parser')

• retrieves and displays the webpage
• This does not display the webpage. BeautufulSoup parses webpage retrieved by urllib.rquest
• parses the html content of the "https://www.nytimes.com" webpage.
• This parses all html tags and contents of the webpage.
• downloads the webpage
• This does not save files to the computer

Q-10: What does the following block of code print?

url = "https://www.nytimes.com/"
html = urllib.request.urlopen(url).read()
soup = BeautifulSoup(html, 'html.parser')

tags = soup('img')
for tag in tags:
    print(tag.get('src', None))

• retrieves and displays the webpage
• urllib retrieves the webpage but does not display it
• downloads the webpage
• this does not save files to the computer
• prints the images from 'www.nytimes.com'
• BeautifulSoup and html.parser cannot display images
• prints all the 'img' sources under 'src' from 'www.nytimes.com'
• it prints out the image sources listed under 'src' of 'img' tags.

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