HDR+ is an image processing pipeline presented by Google in 2016. At its core lies a denoising algorithm that uses a burst of raw images to produce a single higher quality image. Since it is designed as a versatile solution for smartphone cameras, it does not necessarily aim for the maximization of standard denoising metrics, but rather for the production of natural, visually pleasing images. In this article, we specifically discuss and analyze the HDR+ burst denoising algorithm architecture and the impact of its various parameters. With this publication, we provide an open source Python implementation of the algorithm, along with an interactive demo. Source Code The Python implementation of HDR+ has been peer-reviewed and accepted by IPOL. The source code, its documentation, and the online demo are available from the web page of this article. Compilation and usage instructions are included in the README.txt file of the archive. The code is also available on GitHub.