Python Event Hooks for Request and Response Customization

Python urllib3 : Exercise-24 with Solution

Write a Python program that uses event hooks for both requests and responses to customize behavior at various stages of the request/response lifecycle.

Sample Solution:

Python Code :

import urllib3

# Event hook for modifying request headers before sending
def modify_request_headers(request_headers):
    print("Modifying request headers...")
    request_headers['User-Agent'] = 'Custom User-Agent'
    return request_headers

# Event hook for handling response data after receiving
def handle_response(response):
    print("Handling response...")
    print(f"Response status code: {response.status}")
    print("Response data:")

# Create a PoolManager with event hooks
http = urllib3.PoolManager()
http.headers_callback = modify_request_headers
http.response_callback = handle_response

# Define the URL for the request
url = 'https://www.example.com'

    # Make a GET request
    response = http.request('GET', url)
    # Check if the request was successful (status code 200)
    if response.status == 200:
        print("Request Successful!")
        print(f"Error: Unable to fetch data. Status Code: {response.status}")

except Exception as e:
    print(f"Error: {e}")

Sample Output:

Request Successful!


Here's a brief explanation of the above Python urllib3 library code:

  • We define two event hooks: "modify_request_headers" for modifying request headers before sending and "handle_response" for handling response data after receiving.
  • We create a 'PoolManager' object and assign event hooks to "http.headers_callback" and "http.response_callback".
  • When a request is made, the "modify_request_headers()" function is called to modify the request headers before sending.
  • After receiving the response, the "handle_response()" function is called to handle the response data.
  • Finally, we make a GET request to the specified URL, and the defined event hooks are invoked during the request/response lifecycle.


Flowchart: Python Event Hooks for Request and Response Customization.

Python Code Editor :

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Previous: Python Retry Mechanism with incremental timeouts.
Next: Python URL Parsing and Modification for Requests.

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