flask_example.py

"""A simple number and datetime addition JSON API.
Run the app:

    $ python examples/flask_example.py

Try the following with httpie (a cURL-like utility, http://httpie.org):

    $ pip install httpie
    $ http GET :5001/
    $ http GET :5001/ name==Ada
    $ http POST :5001/add x=40 y=2
    $ http POST :5001/subtract x=40 y=2
    $ http POST :5001/dateadd value=1973-04-10 addend=63
    $ http POST :5001/dateadd value=2014-10-23 addend=525600 unit=minutes
"""

import datetime as dt

from flask import Flask, jsonify

from webargs import fields, validate
from webargs.flaskparser import use_args, use_kwargs

app = Flask(__name__)

hello_args = {"name": fields.Str(load_default="Friend")}


@app.route("/", methods=["GET"])
@use_args(hello_args)
def index(args):
    """A welcome page."""
    return jsonify({"message": "Welcome, {}!".format(args["name"])})


add_args = {"x": fields.Float(required=True), "y": fields.Float(required=True)}


@app.route("/add", methods=["POST"])
@use_kwargs(add_args)
def add(x, y):
    """An addition endpoint."""
    return jsonify({"result": x + y})


@app.route("/subtract", methods=["POST"])
@use_kwargs(add_args)
async def subtract(x, y):
    """An async subtraction endpoint."""
    return jsonify({"result": x - y})


dateadd_args = {
    "value": fields.Date(required=False),
    "addend": fields.Int(required=True, validate=validate.Range(min=1)),
    "unit": fields.Str(
        load_default="days", validate=validate.OneOf(["minutes", "days"])
    ),
}


@app.route("/dateadd", methods=["POST"])
@use_kwargs(dateadd_args)
def dateadd(value, addend, unit):
    """A date adder endpoint."""
    value = value or dt.datetime.utcnow()
    if unit == "minutes":
        delta = dt.timedelta(minutes=addend)
    else:
        delta = dt.timedelta(days=addend)
    result = value + delta
    return jsonify({"result": result.isoformat()})


# Return validation errors as JSON
@app.errorhandler(422)
@app.errorhandler(400)
def handle_error(err):
    headers = err.data.get("headers", None)
    messages = err.data.get("messages", ["Invalid request."])
    if headers:
        return jsonify({"errors": messages}), err.code, headers
    else:
        return jsonify({"errors": messages}), err.code


if __name__ == "__main__":
    app.run(port=5001, debug=True)