Docker/Virtualenv

How to create a virtual environment in a Dockerfile: https://pythonspeed.com/articles/activate-virtualenv-dockerfile/

The old way

FROM ubuntu:18.04
RUN apt-get update && apt-get install \
  -y --no-install-recommends python3 python3-virtualenv

RUN python3 -m virtualenv --python=/usr/bin/python3 /opt/venv

# Install dependencies:
COPY requirements.txt .
RUN . /opt/venv/bin/activate && pip install -r requirements.txt

# Run the application:
COPY myapp.py .
CMD . /opt/venv/bin/activate && exec python myapp.py

Note that the exec is there to get correct signal handling.

The better way

FROM ubuntu:18.04
RUN apt-get update && apt-get install \
  -y --no-install-recommends python3 python3-virtualenv

ENV VIRTUAL_ENV=/opt/venv

# ----- lines above are same, lines below are different -----

RUN python3 -m virtualenv --python=/usr/bin/python3 $VIRTUAL_ENV
ENV PATH="$VIRTUAL_ENV/bin:$PATH"

# Install dependencies:
COPY requirements.txt .
RUN pip install -r requirements.txt

# Run the application:
COPY myapp.py .
CMD ["python", "myapp.py"]