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# Contextual Bandits
A plain bandit picks arms from their history alone; a contextual bandit chooses actions using side information too. The page opens with an overview deck and a personalization talk, then a Tools section with the Python packages that implement the idea.
The same notes are in [A/B Testing](/decision-intelligence/a-b-testing.md), [Multi Armed Bandits](/decision-intelligence/multi-armed-bandits.md), and [Reinforcement Learning](/decision-intelligence/reinforcement-learning.md).
The overview is [Contextual bandits](https://drive.google.com/file/d/1EiLlajcSanTE19BOFKOTOlzHJxYSxz7w/view), the Contextual Bandits.pdf deck. It came via [personalization in practice](https://booking.ai/personalization-in-practice-2bb4bc680eb3), the personalization talk it belongs to.
## Tools
After the overview, the question is what to run. [contextualbandits.com](http://web.archive.org/web/20250809185312/https://contextualbandits.com/) is the hosted option — adapt your creative according to context and outcomes automatically without A/B-sitting your campaigns. For code, [Striatum](https://github.com/ntucllab/striatum) is ntucllab/striatum on GitHub, contextual bandits in python.
The fuller package is [Contextual bandits](https://github.com/david-cortes/contextualbandits), in python by David Cortes, and its README says what it is for:
"This Python package contains implementations of methods from different papers dealing with contextual bandit problems, as well as adaptations from typical multi-armed bandits strategies. It aims to provide an easy way to prototype and compare ideas, to reproduce research papers that don't provide easily-available implementations of their proposed algorithms, and to serve as a guide in learning about contextual bandits. For details about the implementations, or if you would like to cite this in your research, see ["Adapting multi-armed bandits policies to contextual bandits scenarios"](https://arxiv.org/abs/1811.04383)."
The figure below is from that package.
Contextual bandits package.
## Deprecated links
{% hint style="warning" %}
These links and images no longer work. The original wording is kept here. A same-resource copy, when one was checked, is used above.
{% endhint %}
* contextualbandits.com — adapt your creative according to context and outcomes automatically without A/B-sitting your campaigns. This address no longer opens:
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