Python ‘requests’ module: TooManyRedirects Exception [Solved]

While developing in Python, encountering exceptions is a common part of the debugging process. One such exception is TooManyRedirects, which can occur when using the requests module to make HTTP requests. This exception indicates that a request exceeded the maximum number of allowed redirections. To understand and resolve this, it’s essential first to comprehend the reasons that trigger the error and then explore the different solutions.

Understanding the Cause

The TooManyRedirects exception happens when the requests module follows a chain of redirects that exceeds its set limit. A redirect loop or an overly-long redirect chain typically causes it. The default maximum limit is set to 30, but this can be configured. Here’s a brief overview of possible causes:

• A redirect loop where the server instructs the client to keep making new requests that never resolve to a final destination.
• An excessively long chain of valid redirects, which surpasses the allowances defined in the requests configurations.
• Incorrect server configurations or URL structures that lead to unresolvable redirections.

Solution 1: Increase Max Redirects Limit

If you believe that the redirect chain is valid and just exceeds the default limit, you can increase the maximum number of redirections allowed. Be cautious with this approach as it might mask an underlying issue.

Steps to implement:

1. Import the requests module in your Python script.
2. Set the limit using the max_redirects parameter within the requests.get() or similar methods.
3. Make our HTTP request with the new limit.

Code example:

import requests

try:
    response = requests.get('http://example.com', max_redirects=50)
    print(response.content)
except requests.TooManyRedirects as e:
    print(e)

Advantages: Relatively straightforward, can resolve the issue if it’s simply a matter of an extensive but expected redirect chain.

Limitations: Might not fix the problem if the redirects are actually part of a loop; you risk getting stuck in a substantial but endless redirection.

Solution 2: Set Allow Redirects to False

To avoid getting caught in redirection loops, you can tell the requests module not to follow redirects at all. This is useful for inspecting the response and diagnosing the issue.

Steps to implement:

1. Import the requests module.
2. Make the HTTP request with parameter allow_redirects=False.
3. Analyze the response HTTP status code and the ‘Location’ header to diagnose the issue.

Code example:

import requests

response = requests.get('http://example.com', allow_redirects=False)
if response.status_code in (301, 302):
    new_location = response.headers['Location']
    print(f'Redirect to {new_location}')
else:
    print(response.content)

Advantages: Prevents the TooManyRedirects exception by cutting down the redirection process early.
Limitations: This approach won’t actually ‘follow’ any redirects, so it might require additional management for handling subsequent requests.

Solution 3: Utilize a Retry Strategy with Backoff

Implementing a custom retry strategy can help to overcome redirection issues. This may involve using a backoff algorithm to avoid hitting the redirect limit and to give more control over the process.

Steps to implement:

1. Import the requests module along with urllib3 or a similar library that can enforce a retry strategy.
2. Define a custom retry strategy with backoff parameters.
3. Mount this strategy onto your HTTP session.
4. Make the HTTP request using this customized session.

Code example:

import requests
from requests.packages.urllib3.util.retry import Retry
from requests.adapters import HTTPAdapter

retry_strategy = Retry(
    total=3,
    status_forcelist=[413, 429, 500, 502, 503, 504],
    method_whitelist=['HEAD', 'GET', 'OPTIONS']
)
adapter = HTTPAdapter(max_retries=retry_strategy)
http = requests.Session()
http.mount('http://', adapter)
http.mount('https://', adapter)

try:
    response = http.get('http://example.com')
    print(response.content)
except requests.exceptions.RequestException as e:
    print(e)

Advantages: Provides a sophisticated method of handling redirects with increased control over the request process.
Limitations: More complex to set up and may introduce additional dependencies into your project.

Solution 4: Verify the URL

A common reason for the TooManyRedirects exception is an incorrect URL structure or server configuration leading to infinite redirection loops. Always verify that the URLs you’re using are correct and fix any errors at the source if possible.