📝 Add note to discourage Alpine with Python (#96)

Author: tiangolo

README.md

@@ -8,11 +8,18 @@
 * [`python3.6` _(Dockerfile)_](https://github.com/tiangolo/uvicorn-gunicorn-docker/blob/master/docker-images/python3.6.dockerfile)
 * [`python3.9-slim` _(Dockerfile)_](https://github.com/tiangolo/uvicorn-gunicorn-docker/blob/master/docker-images/python3.9-slim.dockerfile)
 * [`python3.8-slim` _(Dockerfile)_](https://github.com/tiangolo/uvicorn-gunicorn-docker/blob/master/docker-images/python3.8-slim.dockerfile)
+
+## Discouraged tags
+
 * [`python3.9-alpine3.14` _(Dockerfile)_](https://github.com/tiangolo/uvicorn-gunicorn-docker/blob/master/docker-images/python3.9-alpine3.14.dockerfile)
 * [`python3.8-alpine3.10` _(Dockerfile)_](https://github.com/tiangolo/uvicorn-gunicorn-docker/blob/master/docker-images/python3.8-alpine3.10.dockerfile)
 * [`python3.7-alpine3.8` _(Dockerfile)_](https://github.com/tiangolo/uvicorn-gunicorn-docker/blob/master/docker-images/python3.7-alpine3.8.dockerfile)
 * [`python3.6-alpine3.8` _(Dockerfile)_](https://github.com/tiangolo/uvicorn-gunicorn-docker/blob/master/docker-images/python3.6-alpine3.8.dockerfile)
 
+To learn more about why Alpine images are discouraged for Python read the note at the end: [🚨 Alpine Python Warning](#-alpine-python-warning).
+
+---
+
 **Note**: There are [tags for each build date](https://hub.docker.com/r/tiangolo/uvicorn-gunicorn/tags). If you need to "pin" the Docker image version you use, you can select one of those tags. E.g. `tiangolo/uvicorn-gunicorn:python3.7-2019-10-15`.
 
 # uvicorn-gunicorn
@@ -635,6 +642,24 @@ But these environment variables will work the same as described above:
 * `PORT`
 * `LOG_LEVEL`
 
+## 🚨 Alpine Python Warning
+
+In short: You probably shouldn't use Alpine for Python projects, instead use the `slim` Docker image versions.
+
+---
+
+Do you want more details? Continue reading 👇
+
+Alpine is more useful for other languages where you build a static binary in one Docker image stage (using multi-stage Docker building) and then copy it to a simple Alpine image, and then just execute that binary. For example, using Go.
+
+But for Python, as Alpine doesn't use the standard tooling used for building Python extensions, when installing packages, in many cases Python (`pip`) won't find a precompiled installable package (a "wheel") for Alpine. And after debugging lots of strange errors you will realize that you have to install a lot of extra tooling and build a lot of dependencies just to use some of these common Python packages. 😩
+
+This means that, although the original Alpine image might have been small, you end up with a an image with a size comparable to the size you would have gotten if you had just used a standard Python image (based on Debian), or in some cases even larger. 🤯
+
+And in all those cases, it will take much longer to build, consuming much more resources, building dependencies for longer, and also increasing its carbon footprint, as you are using more CPU time and energy for each build. 🌳
+
+If you want slim Python images, you should instead try and use the `slim` versions that are still based on Debian, but are smaller. 🤓
+
 ## Tests
 
 All the image tags, configurations, environment variables and application options are tested.