add simple python webapp example

python/Dockerfile

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+# Use an official Python runtime as a parent image
+FROM python:2.7-slim
+
+# Set working directory to /app
+WORKDIR /app
+
+# Copy the current directory contents into the container at /app
+ADD . /app
+
+# Install any needed packages specified in requirements.txt
+RUN pip install --trusted-host pypi.python.org -r requirements.txt
+
+# Make port 80 available to the world outside this container
+EXPOSE 80
+
+# Define environment variable
+ENV NAME World
+
+# Run app.py when the container launches
+CMD ["python", "app.py"]

python/app.py

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+from flask import Flask
+from redis import Redis, RedisError
+import os
+import socket
+
+# Connect to Redis
+redis = Redis(host="redis", db=0, socket_connect_timeout=2, socket_timeout=2)
+
+app = Flask(__name__)
+
+@app.route("/")
+def hello():
+    try:
+        visits = redis.incr("counter")
+    except RedisError:
+        visits = "<i>cannot connect to Redis, counter disabled</i>"
+
+    html = "<h3>Hello {name}!</h3>" \
+           "<b>Hostname:</b> {hostname}<br/>" \
+           "<b>Visits:</b> {visits}"
+    return html.format(name=os.getenv("NAME", "world"), hostname=socket.gethostname(), visits=visits)
+
+if __name__ == "__main__":
+    app.run(host='0.0.0.0', port=80)

python/readme.txt

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+# create docker image and tag it using -t
+docker build -t friendlyhello .
+
+# new docker image should show up in local Docker image registry
+docker image ls
+
+# run app in container and map local machine's port 4000 to container's published port 80 using -p
+docker run -p 4000:80 friendlyhello
+
+# open http://localhost:4000 in local machine's browser
+
+# quit app with CTRL+C
+
+# explictly stop container (on Windows only)
+docker container ls
+docker container stop <container_name or container_id>
+
+# run app in background, in detached mode using -d
+docker run -d -p 4000:80 friendlyhello

python/requirements.txt

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+Flask
+Redis