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Tuesday, February 2nd 2021

Correcting Request URLs with Python Serverless Functions

Posted by

Avatar for tootallnate

Nathan Rajlich

Software Engineer

At the moment, the URLs of incoming requests to Python Serverless Functions deployed on Vercel are decoded automatically.

Because this behavior is not consistent with a "standalone" Python server, Vercel will stop decoding them for newly created Serverless Functions starting March 2nd, 2021. Existing Deployments will not be affected.

As an example, take a look at the Python Serverless Function code shown above and imagine that the URL of the incoming request ends in /hi%21:

  • With the incorrect behavior, self.path will be set to /hi!.
  • With the updated correct behavior, self.path will be set to /hi%21, which matches the behavior of the built-in HTTPServer class in Python.

To try out this change, define a FORCE_RUNTIME_TAG Environment Variable for your project, set it to canary and create a new Deployment.