simplify Dockerfile

Dockerfile

@@ -1,47 +1,21 @@
-FROM python:3.10-alpine
+# Python image.
+# - https://docs.docker.com/language/python/build-images/
+FROM python:3.10-slim-buster
 
 WORKDIR /usr/src/
 
-# setting the correct timezone requires "zdtata"
-# numpy (dependency of matplotlib) requires "make automake gcc ..."
-#   source: https://stackoverflow.com/a/48349161/6334421
-# pillow (dependency of matplotlib) requires "zlib-dev jpeg-dev ..."
-RUN apk update && \
-    apk add \
-        tzdata \
-        make automake gcc g++ subversion python3-dev \
-        zlib-dev jpeg-dev freetype-dev lcms2-dev libwebp-dev tcl-dev tk-dev harfbuzz-dev \
-          fribidi-dev libimagequant-dev libxcb-dev && \
-    rm -rf /var/cache/apk/*
-
-# source: https://serverfault.com/a/683651/537998
-ENV TZ=Europe/Berlin
-RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone
-
-RUN python3 -m pip install --no-cache-dir --upgrade pip
-
-# LDFLAGS required for "pip install pillow"
-# otherwise this would be necessary:
-## RUN ln -s /usr/lib/x86_64-linux-gnu/libz.so /lib/
-## RUN ln -s /usr/lib/x86_64-linux-gnu/libjpeg.so /lib/
-# source: https://github.com/python-pillow/Pillow/issues/3103#issuecomment-382634946
-ENV LDFLAGS=-L/usr/lib/x86_64-linux-gnu/
+# Set timezone.
+# - https://dev.to/0xbf/set-timezone-in-your-docker-image-d22
+# Official Debian and Ubuntu images automatically run apt-get clean, so explicit invocation is not required.
+# - https://docs.docker.com/develop/develop-images/dockerfile_best-practices/#run
+RUN apt update && apt install tzdata -y
+ENV TZ="Europe/Berlin"
 
 COPY requirements.txt ./
-RUN python3 -m pip install --no-cache-dir --upgrade -r requirements.txt
-#
-# if the above fails, try using the below instead
-#
-#RUN python3 -m pip install --no-cache-dir --upgrade requests
-#RUN python3 -m pip install --no-cache-dir --upgrade setuptools
-#RUN python3 -m pip install --no-cache-dir --upgrade numpy
-#RUN python3 -m pip install --no-cache-dir --upgrade pillow
-#RUN python3 -m pip install --no-cache-dir --upgrade matplotlib
+RUN pip3 install --no-cache-dir -r requirements.txt
 
 COPY src/ ./
 RUN chmod +x langfingaz/main.py
 
-# unbuffered output option otherwise script sleeps before any output appears
-# python -u
-ENTRYPOINT [ "python", "./langfingaz/main.py" ]
+ENTRYPOINT [ "python3", "./langfingaz/main.py" ]
 CMD [ "log-verbose" ]