Python 3 virtualenv and Docker - python-3.x

Question

I'm trying to build a docker image with python 3 and virtualenv.
I understand that I wouldn't need to use wirtualenv in a docker image as I'm going to use only python 3, yet I see some clean isolation benefits of using virtualenv anyways.
What's the best practice? Should I avoid using virtualenv on docker?
If that's the case, how can I setup python3 and pip3 to be used as python and pip (without the 3)?
This is my Dockerfile:
FROM openjdk:8-alpine
RUN apk update && apk add bash gcc musl-dev
RUN apk add python3 python3-dev
RUN apk add py3-pip
RUN apk add libxslt-dev libxml2-dev
ENV PROJECT_HOME /opt/app
RUN mkdir -p /opt/app
RUN mkdir -p /opt/app/modules
ENV LD_LIBRARY_PATH /usr/lib/python3.6/site-packages/jep
ENV LD_PRELOAD /usr/lib/libpython3.6m.so
RUN pip3 install jep
RUN pip3 install ads
RUN pip3 install gspread
RUN pip3 list
COPY target/my-server-1.0-SNAPSHOT.jar $PROJECT_HOME/my-server-1.0-SNAPSHOT.jar
WORKDIR $PROJECT_HOME
CMD ["java", "-Dspring.data.mongodb.uri=mongodb://my-mongo:27017/mydb","-jar","./my-server-1.0-SNAPSHOT.jar"]
Thanks
=== UPDATE 1 ===
I'm trying to create a new virtual env in the WORKDIR, install some libs and then execute a shell script, even though I see it creates the whole thing when I build the image, when running the container the environment folder is empty.
This is from my Dockerfile:
RUN virtualenv ./env && source ./env/bin/activate && pip install jep \
googleads gspread oauth2client
ENTRYPOINT ["/bin/bash", "./startup.sh"]
startup.sh:
#!/bin/sh
source ./env/bin/activate
java -Dspring.data.mongodb.uri=mongodb://my-mongo:27017/mydb -jar ./my-server-1.0-SNAPSHOT.jar
It builds fine but on docker-compose up -d this is the output:
./startup.sh: source: line 2: can't open './env/bin/activate'
The env folder exists, but it's empty.
Any ideas?
Thanks!
=== UPDATE 2 ===
This is the working config:
RUN virtualenv ./my-env && source ./my-env/bin/activate \
&& pip install gspread==0.6.2 jep oauth2client googleads pandas
CMD ["/bin/bash", "-c", "./startup.sh"]
This is startup.sh:
#!/bin/sh
source ./my-env/bin/activate
java -Dspring.data.mongodb.uri=mongodb://my-mongo:27017/mydb -jar ./my-server-1.0-SNAPSHOT.jar

Answer 1

I don't think using virtualenv in docker is something really negative, it will slow down your container builds just a bit.
As for renaming pip3 and python3, you can create a hard link like this:
ln /usr/bin/python3 /usr/bin/python
ln /usr/bin/pip3 /usr/bin/pip
assuming python3 executable is in /usr/bin/. You can find its location by running which python3
P.S.: Your dockerfile contains loads of RUN instructions, that are creating unnecessary intermediate containers. Combine them to save space and time:
RUN apk update && apk add bash gcc musl-dev \
python3 python3-dev py3-pip \
libxslt-dev libxml2-dev
RUN mkdir -p /opt/app/modules # you don't need the first one, -p will create it for you
RUN pip3 install jep ads gspread
Or combine them even further, if you aren't planning to change them often:
RUN apk update
&& apk add bash gcc musl-dev \
python3 python3-dev py3-pip \
libxslt-dev libxml2-dev \
&& mkdir -p /opt/app/modules \
&& pip3 install jep ads gspread

Answer 2

The only "workaround" I've found in order to use virtualenv from my docker container is to enter to the docker by ssh, create the environment, install the libs and set its folder as a volume in the docker-compose config so it won't be deleted and I can use it afterward.
(Or to have it ready and just copy the folder at build time) which could be a good option for saving build time, isn't it?
Otherwise, If I create it on Dockerfile and install the libs there, its folder gets empty when the container runs. Don't know why.
I appreciate if anyone can suggest a better way to deal with that.