Add sample flask application.

Author: nitinl

flask-app/.gitignore

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+*.sqlite

flask-app/README.md

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+# Example Flask app
+
+### Setting up
+1. Create a Python3 virtual environment and activate it.
+2. Install dependencies by running: `pip install -r requirements.txt`
+3. Initialize db by running: `python library_app/models.py`
+
+### Running the app
+```python run.py```
+
+### Guide to the code:
+1. The API requests are defined in views.py
+2. All the database models are defined in models.py

flask-app/library_app/__init__.py

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+"""
+Description: Setup the flask application.
+"""
+from flask import Flask
+from flask_sqlalchemy import SQLAlchemy
+
+app = Flask(__name__)
+app.secret_key = 'dev'
+
+# enter path to the sqlite file here. A new db is created if one does not exist.
+app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///library.sqlite'
+
+db = SQLAlchemy(app)
+from library_app import models
+from library_app import views

flask-app/library_app/author.py

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+"""
+Description: Functions related to Author
+"""
+from library_app import db
+from library_app.models import Author
+
+
+def get_all(filters):
+    allowed_filters = ['name', 'country', 'year_of_birth']
+    final_filters = {k: v for k, v in filters.items() if k in allowed_filters}
+    authors = Author.query.filter_by(**final_filters).all()
+    return authors
+
+
+def get(author_id):
+    return Author.query.filter_by(id=author_id).first()
+
+
+def create(name, country=None, year_of_birth=None):
+    new_author = Author(name=name, country=country, year_of_birth=year_of_birth)
+    db.session.add(new_author)
+    db.session.commit()
+
+
+def update(author_id, fields):
+    result = Author.query.filter_by(id=author_id).update(fields)
+    db.session.commit()
+    return result
+
+
+def delete(author):
+    db.session.delete(author)
+    db.session.commit()

flask-app/library_app/models.py

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+"""
+Description: Models: Classes representing DB tables.
+"""
+from library_app import db
+
+from sqlalchemy.inspection import inspect
+
+
+class Serializer(object):
+    """Class for serializing SQLAlchemy objects into dicts."""
+
+    def serialize(self):
+        return {c: getattr(self, c) for c in inspect(self).attrs.keys()}
+
+    @staticmethod
+    def serialize_list(list_obj):
+        return [m.serialize() for m in list_obj]
+
+
+class Author(db.Model, Serializer):
+    # See http://flask-sqlalchemy.pocoo.org/2.0/models/#simple-example
+    # for details on the column types.
+    id = db.Column(db.Integer, primary_key=True)
+    name = db.Column(db.String(120), nullable=False)
+    country = db.Column(db.String(80))
+    year_of_birth = db.Column(db.Integer)
+
+    def __repr__(self):
+        return f'Author name:{self.name} country:{self.country} year: {self.year_of_birth}'
+
+
+if __name__ == '__main__':
+    db.create_all()
+    db.session.commit()

flask-app/library_app/utils.py

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+"""
+Description: Util functions.
+"""
+
+
+def werkzeug_rule_endpoint(rule):
+    tmp = []
+    for is_dynamic, data in rule._trace:
+        if is_dynamic:
+            tmp.append(u"<%s>" % data)
+        else:
+            tmp.append(data)
+    return repr((u"".join(tmp)).lstrip(u"|")).lstrip(u"u")

flask-app/library_app/views.py

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+"""
+Description: Requests supported by the flask app.
+"""
+import sqlalchemy
+from flask import jsonify, request, make_response
+
+from library_app import app, author, utils
+from library_app.models import Author
+
+
+@app.route('/')
+def index():
+    return "Welcome to Library app"
+
+
+@app.route('/site-map')
+def site_map():
+    urls = {utils.werkzeug_rule_endpoint(url): str(url.methods) for url in app.url_map.iter_rules()}
+    return jsonify(urls)
+
+
+@app.route('/author', methods=['GET', 'POST'])
+def authors_view():
+    if request.method == 'GET':
+        authors = author.get_all(filters=request.args)
+        return jsonify(data=Author.serialize_list(authors))
+
+    if request.method == 'POST':
+        try:
+            author.create(name=request.json['name'],
+                          country=request.json.get('country'),
+                          year_of_birth=request.json.get('year_of_birth'))
+            return make_response(jsonify(response='OK'), 201)
+        except sqlalchemy.exc.InvalidRequestError:
+            return make_response(jsonify(error='Bad request'), 400)
+
+
+@app.route('/author/<int:author_id>', methods=['GET', 'PUT', 'PATCH', 'DELETE'])
+def author_view(author_id):
+    author_result = author.get(author_id)
+    if author_result is None:
+        return make_response(jsonify(response=f'Author with id {author_id} not found'), 404)
+
+    if request.method == 'GET':
+        return jsonify(author_result.serialize())
+
+    if request.method == 'DELETE':
+        author.delete(author_result)
+        return jsonify(response='OK')
+
+    if request.method in ['PUT', 'PATCH']:
+        try:
+            if request.method == 'PATCH':
+                fields = request.json
+            else:  # for PUT request, use default values for empty fields
+                fields = {'name': request.json['name'],
+                          'country': request.json.get('country'),
+                          'year_of_birth': request.json.get('year_of_birth')}
+            author.update(author_id, fields)
+            return jsonify(response='OK')
+
+        except (sqlalchemy.exc.InvalidRequestError, KeyError):
+            return make_response(jsonify(error='Bad request'), 400)

flask-app/requirements.txt

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+click==7.1.2
+Flask==1.1.2
+Flask-SQLAlchemy==2.4.4
+itsdangerous==1.1.0
+Jinja2==2.11.2
+MarkupSafe==1.1.1
+SQLAlchemy==1.3.20
+Werkzeug==1.0.1

flask-app/run.py

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+"""
+Description: Script for starting the flask application. Usage: $ python run.py
+"""
+from library_app import app
+
+
+# If you want some code to not be executed when this file is imported, but only
+# when this file is run as "python filename.py", then put it under __name__=='__main__'.
+# More about this here: https://stackoverflow.com/a/419185
+if __name__ == '__main__':
+    app.run(debug=True)