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Python Charmers Coffee Reviews

This is the Python Charmers Coffee Shop application.

Really fast getting started

  1. Get the .env file from the trainers. This is configured for minimal configuration

  2. In the .env file change your DB_NUMBER setting (at the top of the file) to either your personal DB number or your group number.

  3. Create a new virtual environment:

    python3 -m venv venv

  4. Activate the virtual environment

    OS Command
    Windows venv/bin/activate
    OS X / *nix source venv/bin/activate

  5. Install the application requirements

    pip install -r requirements.txt
pip install -r dev_requirements.txt

  6. Set the FLASK_APP environment variabls

    OS Command
    Windows set FLASK_APP=server
    OS X / *nix export FLASK_APP=server

  7. Upgrade the database with flask db upgrade

  8. Run the application locally with flask run

Really fast deploymnet to AWS

  1. Install Zappa with pip install zappa (if you're using Python 3.7 use pip install git+https://github.com/itamt/Zappa.git)
  2. Run zappa init to initialise the zappa application.
    • The app's functon will be server.app
    • For now select n when asked if you want to deploy globally
  3. Run zappa deploy dev to deploy the application
  4. Test the application by visiting the URL you're provided

Getting Started

Create and activate a virtual environment, and then install the requirements:

pip install -r requirements.txt
pip install -r dev_requirements.txt

Copy sample environment file from the environment_config folder into a file .env in the base folder:

cp environment_config/sample.env .env

Setting up environment variables

The following environment variables should be updated in the .env files:

Variable Description
SECRET_KEY The application secret key. You could use `python3 -c "import os; print(os.urandom(48))"
SQLALCHEMY_DATABASE_URL The SQLAlchemy connection string. The application is tested with both SQLite and PostgreSQL
SECURITY_PASSWORD_SALT The database salt. Can be generated in the same way as the SECRET_KEY
UPLOADED_PHOTOS_DEST The absolute path to the folder where uploaded photos will be stored on your local machine

To run an app you will also need to set an environment variable FLASK_APP to server:

export FLASK_APP=server

Create DB

You can use Alembic to set up the database:

flask db upgrade

AWS

Ultimately this application is intended to be deployed on AWS. As such there's a dependency on the boto3 library. The application will work locally provided you have boto3 installed, but for uploading files to S3 and deployment to AWS Lambda you will need the AWS CLI installed and configured.

Installing the AWS CLI is easy (if you wish there is complete documentation available as well):

  1. Outside your Virtual Environment (to install globally on your system) run: 
    pip3 install awscli
  2. Copy your AWS Access Key ID and your AWS Secret Access Key from your IAM role in the AWS management console
  3. From the command line run: 
    aws configure
    to complete the configuration process
  4. Test the configuration by running: 
    aws s3 ls
    to list all of your S3 buckets along with their unique identifiers

Runing the application locally

You can run the server locally using the standard flask comands.

flask run

Extended exercises

There will be an extended exercises per day based on the coffee shop application.

The solutions will be separated into individual branches (in the form day_n_exercise), and there is a combined_solutions branch where all extended exercises are merged together.

Day 2 Extended exercise: Templating

The front page of the coffee shop application is very bare at the moment. We can do better:

  1. Update the / endpoint to display the 10 most recently added shops.

    Since we haven't covered SQLAlchemy yet, use the following to generate shops to pass through to the template:

    from coffeeshop.server.shop.models import Shop
shops = Shop.query.order_by(Shop.date_added.desc()).limit(10)

  2. Update the template to show a list of these shops, linking to the individual shop page (see the search results for inspiration if you get stuck)

Day 3 Extended exercise: API Access

It would be nice to create an API for people to programatically query the coffee shops, rather than having to scrape the site.

Use Connexion to create a simple API to access the Shops model. It should have two endpoints:

  1. A list endpoint which lists stores 10 at a time. It should take a page parameter which defaults to 1 and can be any positive integer, which is the query offset for which stores to return.
  2. A search endpoint which lists stores matching a query passed via the q parameter, in the same way the current coffeeshop.server.shop.views.search_shop method handles queries. It should also take a page parameter.

The functions that are mapped by the app.yaml file should be store in coffeeshop/server/shop/api.py

You will also need to create a new create_connexion_app method within your coffeeshop/server/__init__.py file.

Day 4 Extended exercise: Cleaning up your code

Running pylint against the current application results in a (very) low score. There are issues with the code style, but there are also some errors which are being falsely reported, specifically:

  • E1101 (instance of object doesn't have member)
  • R0401 (circular imports)

Generate a .pylintrc file for your project with:

pylint --generate-rcfile > .pylintrc

In the .pylintrc file add those two errors to the disabled messages list.

Re-run pylint and update the files so that the score is at least 8 out of 10.

Day 5 extended exercise: Preparation for deployment

Prepping your application for deployment

To deploy to AWS Lambda you'll need:

  1. To have the AWS CLI installed and configured
  2. To install Zappa (if you're using Python 3.7 use pip install git+https://github.com/itamt/Zappa.git)
  3. You will need a database setup on RDS where the application data will be stored - the connection string for an accessible PostGreSQL database will be provided via a download link by the trainers.
  4. You'll need to create a new bucket on S3 to store photos. It should not block public ACLs from uploading. It will be used to store uploaded photos.
  5. You'll need to update the following environment variables in your .env file (note: it's a good idea to backup your development .env file first - possibly with cp .env environment_config/dev.env):
    • SECRET_KEY should be generated for production as per the instructions above
    • SECURITY_PASSWORD_SALT likewise the password salt should be updated
    • SQLALCHEMY_DATABASE_URI the connection string for your RDS database
    • FLASK_ENV should now be set to production
    • WTF_CSRF_ENABLED should be True
  6. Run the Alembic upgrade to add your database tables on the server

Photos in S3

Your goal is to upload photos to a S3 bucket. As such you'll need to update your S3 settings accordingly (in your .env file):

Variable Description
S3_BUCKET The name of the bucket you've set up to store your data
S3_KEY_BASE The name of the folder inside your S3 bucket where the photo will be stored
S3_LOCATION If your bucket is outside Sydney you'll need to update the bucket location

Finally, to ensure the upload works, set the environment variable that will control your app:

On Windows:

set APP_SETTINGS="coffeeshop.server.config.ProductionConfig"

On Unix or OS X:

export APP_SETTINGS="coffeeshop.server.config.ProductionConfig"

Then run the app as normal. Test that when you create a new shop and add a photo that instead of being stored locally, the file is uploaded to your S3 bucket.