how to use pip to install pkg from requirement fil

Question

I am trying to build an Docker image. My Dockerfile is like this:

FROM python:2.7
ADD . /code
WORKDIR /code
RUN pip install -r requirement.txt
CMD ["python", "manage.py", "runserver", "0.0.0.0:8300"]

And my requirement.txt file like this:

wheel==0.29.0
numpy==1.11.3
django==1.10.5
django-cors-headers==2.0.2
gspread==0.6.2
oauth2client==4.0.0

Now, I have a little change in my code, and i need pandas, so i add it in to requirement.txt file

wheel==0.29.0
numpy==1.11.3
pandas==0.19.2
django==1.10.5
django-cors-headers==2.0.2
gspread==0.6.2
oauth2client==4.0.0

pip install -r requirement.txt will install all packages in that file, although almost of them has installed before. My question is how to make pip install pandas only? That will save the time to build image.

Thank you

Answer 1

If you rebuild your image after changing requirement.txt with docker build -t <your_image> ., I guess it cann't be done because each time when docker runs docker build, it'll start an intermediate container from base image, and it's a new environment so pip obviously will need to install all of dependencies.

You can consider to build your own base image on python:2.7 with common dependencies pre-installed, then build your application image on your own base image. Once there's a need to add more dependencies, manually re-build the base image on the previous one with only extra dependencies installed, and then maybe optionally docker push it back to your registry.

Hope this could be helpful :-)