Requests is a popular Python library for making HTTP requests. It provides a convenient and high-level interface for sending and receiving data over the web. One powerful feature of Requests is its ability to handle custom request processing through the use of hooks.

What are Hooks?

Hooks in Requests are callback functions that can be registered to be executed at various stages during the lifespan of a request. These hooks allow you to modify the request or response, handle errors, or perform additional processing.

There are four main types of hooks available in Requests:

1. pre_request: Called before the request is sent.
2. post_request: Called after the request is sent but before the response is received.
3. response: Called after the response is received.
4. exception: Called if an exception occurred during the request.

These hooks are defined as Python functions and can be registered using the hooks parameter when making a request.

Example Usage

Let’s take a look at some examples of how hooks can be used in Requests.

Pre-request Hook

The pre-request hook allows you to modify the request before it is sent. For example, you can set custom headers, add authentication tokens, or modify the request body.

import requests

def modify_request(request):
    request.headers['Authorization'] = 'Bearer my_token'

response = requests.get('https://api.example.com', hooks={'pre_request': modify_request})

In this example, the modify_request function adds an Authorization header to the request before it is sent. The hook function is registered using the hooks parameter in the get request.

Post-request Hook

The post-request hook allows you to perform additional processing on the response before it is returned. For example, you can parse the response, log the result, or raise an exception based on the response status code.

import requests

def handle_response(response):
    if response.status_code == 200:
        # Perform processing on the response
        pass
    else:
        # Raise an exception or handle the error
        pass

response = requests.get('https://api.example.com', hooks={'post_request': handle_response})

In this example, the handle_response function checks the status code of the response and performs appropriate actions based on the result. The hook function is registered using the hooks parameter in the get request.

Exception Hook

The exception hook allows you to handle exceptions that may occur during the request. For example, you can log the error or retry the request.

import requests

def handle_exception(exception):
    # Handle the exception
    pass

try:
    response = requests.get('https://api.example.com', hooks={'exception': handle_exception})
except requests.exceptions.RequestException as e:
    # Handle the exception
    pass

In this example, the handle_exception function is called if an exception occurs during the request. The hook function is registered using the hooks parameter in the request. The requests.exceptions.RequestException is a base exception class that captures all exceptions that may occur during a request.

Conclusion

Hooks in Requests provide a powerful way to customize request processing and add additional functionality to your HTTP requests. By using hooks effectively, you can have fine-grained control over the request and response lifecycle.

So next time you’re using Requests in your Python projects, consider using hooks to handle custom request processing and elevate your HTTP interactions to the next level.