Networking in Python – Part 2

In our prior post, we covered the topic of networking within the context of Python programming. In this post, we will further delve into this subject.

URL

A URL (Uniform Resource Locator) is used to specify the address of a resource or information on the internet. It consists of four parts:

1. The protocol to use, such as http:// or https://.
2. The server name or IP address of the server where the resource is located, like www.google.com.
3. An optional port number, indicated by a colon followed by the port number (e.g., :80).
4. The file being referred to, usually indicated by its file name and location, such as /index.html or /home.html.

To extract the various components of a URL in Python, we can utilize the urlparse() function from the urllib.parse module. By passing the URL string as an argument to this function, it will return a tuple containing the individual parts of the URL.

An example implementation of this process is as follows:

import urllib.parse

url_string = 'http://www.example.com/index.html'

parsed_url = urllib.parse.urlparse(url_string)

print(parsed_url)

Output:

ParseResult(scheme='http', netloc='www.example.com', path='/index.html', params='', query='', fragment='')

In the above code, parsed_url will be a tuple object containing the parsed components of the given URL.

To access the different components of a URL that have been parsed into a tuple, we can use specific attributes to extract the desired information. These attributes include:

• scheme: returns the protocol specified in the URL.
• netloc: returns the domain name or IP address of the server, as well as any port number specified.
• path: returns the path of the web page or resource.
• port: returns the port number specified in the URL.

To retrieve the complete URL from the tuple, we can use the geturl() function.

Here is an example implementation that demonstrates these concepts:

import urllib.parse

url_string = 'http://www.example.com:8080/index.html'

parsed_url = urllib.parse.urlparse(url_string)

print(f"Scheme: {parsed_url.scheme}")
print(f"Netloc: {parsed_url.netloc}")
print(f"Path: {parsed_url.path}")
print(f"Port: {parsed_url.port}")

full_url = parsed_url.geturl()
print(f"Full URL: {full_url}")

Output:

Scheme: http
Netloc: www.example.com:8080
Path: /index.html
Port: 8080
Full URL: http://www.example.com:8080/index.html

In the above code, scheme, netloc, path, and port will contain the relevant information from the given URL. full_url will be a string containing the complete URL.

How to read the source code of a webpage from the internet?

To retrieve the source code of a webpage in Python, we can use the urlopen() function from the urllib.request module. This function takes a URL as its argument and returns a file-like object containing the source code of the webpage.

import urllib.request
import ssl
ssl._create_default_https_context = ssl._create_unverified_context


url = "https://www.python.org/"
file = urllib.request.urlopen(url)

html = file.read()
print(html)

In this code, we use urlopen() to open the webpage specified by the URL string url and store it in the file variable. We then read the contents of the file object using the read() method and store it in the html variable. Finally, we print the contents of html to the console.

Please note that the contents of the webpage will be printed to the console as a bytes object, which can be converted to a string using the .decode() method if necessary. Additionally, an internet connection is required to run this code

How to download a web page from the Internet?

In Python, we can download and save a webpage from the internet by following these steps:

1. Ensure that our computer is connected to the internet.
2. Use the urlopen() function to open the desired webpage. This function returns a file-like object containing the contents of the webpage.
3. Read the contents of the file-like object using the read() method and store the data in a variable.
4. Open a new file in binary write mode and write the webpage data to the file.

Here’s an example code snippet that demonstrates these steps:

import urllib.request
import ssl
ssl._create_default_https_context = ssl._create_unverified_context

# Open the desired webpage and read its contents
url = "https://www.python.org"
file = urllib.request.urlopen(url)
content = file.read()

# Open a new file in binary write mode and write the webpage contents to the file
with open('webpagefrominternet.html', 'wb') as f:
    f.write(content)

In this code, urlopen() is used to open the webpage specified by the url variable, and the contents of the webpage are read into the content variable using the read() method. The open() function is then used to create a new file in binary write mode, and the contents of the webpage are written to the file using the write() method.

Please note that this code will only download the HTML content of the webpage, and not any images or other media files that may be present. Additionally, the urlopen() function may raise a urllib.error.HTTPError if the webpage is not found.

How to download an image from Internet?

In Python, we can easily download image files like .jpg, .gif, or .png files from the internet and save them to our computer by using the urlretrieve() function from the urllib.request module.

To use urlretrieve(), we simply need to pass the URL of the image file and the desired filename for the downloaded image as arguments. The function will then download the image from the specified URL and save it to our computer with the specified filename.

Here’s an example implementation of this process:

import urllib.request
import ssl
ssl._create_default_https_context = ssl._create_unverified_context

url = 'https://upload.wikimedia.org/wikipedia/commons/3/32/Googleplex_HQ_%28cropped%29.jpg'

filename = 'myimage.jpg'

urllib.request.urlretrieve(url, filename=filename)

In this code, we specify the URL of the image file we wish to download and the filename we want to save it under. We then use the urlretrieve() function to download the image from the specified URL and save it to our computer with the specified filename.

Please note that an internet connection is required to run this code, and that the urlretrieve() function may raise an exception if there are any errors during the download process.