There’s a lovely Python module for making HTTP requests, called requests. We use it at Luminoso. A bunch of code we depend on uses it. Our API customers use it. Basically everyone uses it because it’s the right thing to use.
Yesterday we did our first code update of the new year on our development systems, and found that suddenly nothing was working. Meanwhile, our customers sent us bug reports for similar reasons. We’d see errors like this one:
TypeError: session() takes no arguments (1 given)
And all kinds of code would crash with this kind of error, which occurs because Requests changed .json from a property to a method:
TypeError: 'instancemethod' object has no attribute '__getitem__'
You see, on December 17, Kenneth Reitz released version 1.0 of requests and declared “This is not a backwards compatible change.” As far as we can tell, this has caused a small ripple of version-related panic in the Python world. We know it’s okay to break compatibility when changing the major version number. That’s what major version numbers are for. But the problem is that it’s really hard to deal with multiple incompatible versions of the same Python package.
If you were to type pip install requests now, you’ll get version 1.0, and it won’t work with most code written for version 0.14. So maybe you should ask for “requests < 1.0″ or “requests == 0.14.2″, and maybe even declare that dependency in setup.py. That was certainly the stopgap measure we went around applying yesterday.
The problem is that, once you do that, you can’t ever upgrade to Requests 1.0 or install any code that uses Requests 1.0, unless you port all your code and update all your Python environments at once. Not even virtualenv will help. You just can’t have an environment that depends on “requests < 1.0″ and “requests >= 1.0″ at the same time and have your code keep working.
The requests-transition package
We want to make it possible to move to the shiny new Requests 1.x code. But we
also want our code stack to keep working in the present. That’s the purpose of
requests-transition. All it does is it installs both versions of
requests as two different packages with different names.
The slogan of requests is “Python HTTP for Humans”. The slogan of requests-transition is “Python HTTP for busy people who don’t have time to port all their code yet”.
To install it using pip:
pip install requests-transition
Now you can stabilize your existing code that uses requests 0.x by changing the line
import requests0 as requests
When you port the code to use requests 1.0, change the import line to:
import requests1 as requests
In the future, when all your dependencies use requests 1.0 and 0.x is a distant memory, you should get the latest version of the real requests package and change the import lines back to:
And that is how you transition to requests 1.x, calmly and painlessly.
We have already updated our API client code to use requests-transition, instead of forcing you to install “requests < 1.0".