Build Docker image of a Python Flask app

Question

I'm trying to build a Docker image for a Python Flask app but having build problems - all files live in a folder called web - this is the project structure:

web/
    __init__.py
    app.py
    Dockerfile
    models.py
    requirements.txt

and app.py at the moment looks like this:

from flask import Flask


app = Flask(__name__)

@app.route("/")
def hello_world():
    return "Hello World!"


if __name__ == "__main__":
    app.run(debug=True,host='0.0.0.0')

I've borrrowed the Dockerfile from https://www.smartfile.com/blog/dockerizing-a-python-flask-application/:

FROM ubuntu:14.04

# Update OS
RUN sed -i 's/# \(.*multiverse$\)/\1/g' /etc/apt/sources.list
RUN apt-get update
RUN apt-get -y upgrade

# Install Python
RUN apt-get install -y python-dev python-pip

# Add requirements.txt
ADD requirements.txt /webapp

# Install wsgi Python web server
RUN pip install uwsgi
# Install app requirements
RUN pip install -r requirements.txt

# Create app directory
ADD . /webapp

# Set the default directory for our environment
ENV HOME /webapp
WORKDIR /webapp

# Expose port 8000 for uwsgi
EXPOSE 8000

ENTRYPOINT ["uwsgi", "--http", "0.0.0.0:8000", "--module", "app:app", "--processes", "1", "--threads", "8"]

I'm trying to build the Docker image using docker build --no-cache --rm -t flask-app, but it ends with an error message:

Successfully installed uwsgi
Cleaning up...
 ---> 9bbc004212a3
Removing intermediate container 70ed8f07c408
Step 8/13 : RUN pip install -r requirements.txt
 ---> Running in f5e2eb59ffd1
Could not open requirements file: [Errno 2] No such file or directory: 'requirements.txt'
Storing debug log for failure in /root/.pip/pip.log
The command '/bin/sh -c pip install -r requirements.txt' returned a non-zero code: 1

Answer 1

I think a very small change on your Dockerfile would fix this:

FROM ubuntu:14.04

# Update OS
RUN sed -i 's/# \(.*multiverse$\)/\1/g' /etc/apt/sources.list
RUN apt-get update
RUN apt-get -y upgrade

# Install Python
RUN apt-get install -y python-dev python-pip

# Add requirements.txt
# Create app directory
ADD . /webapp

# Install wsgi Python web server
RUN pip install uwsgi
# Install app requirements
# Full path to requirements
RUN pip install -r /webapp/requirements.txt

# Set the default directory for our environment
ENV HOME /webapp
WORKDIR /webapp

# Expose port 8000 for uwsgi
EXPOSE 8000

ENTRYPOINT ["uwsgi", "--http", "0.0.0.0:8000", "--module", "app:app", "--processes", "1", "--threads", "8"]

I just added the full path to requirements.txt, this could be accomplished in several different ways, like copying the entire directory folder and then building it.