Some of my favorite little utility methods useful with Flask api development.

flask_utils.py

import json
import datetime

from functools import wraps

from flask import request, jsonify

class ISO8601Encoder(json.JSONEncoder):
  def default(self, obj):
    if isinstance(obj, datetime.datetime):
      return obj.date().isoformat()

    if isinstance(obj, datetime.date):
      return obj.isoformat()

    return super(ISO8601Encoder, self).default(obj)


def jsonify_exception(e):
  return jsonify({
    'error': e.__class__.__name__,
    'message': e.message or e.__class__.__doc__
  })


def parameters_from_request():
  return request.json if request.method == 'POST' else request.args


def require_params(*required_parameters):
  def outer(func):
    @wraps(func)
    def decorated(*args, **kwargs):
      parameters = set(parameters_from_request().keys())
      missing = set(required_parameters) - parameters
      if missing:
        return jsonify({ 'error': 'missing-keys', 'message': 'Missing required parameters: %s' % ', '.join(missing) }), 400
      return func(*args, **kwargs)
    return decorated
  return outer


def validate_contract(contract, data):
  """
  Given a contract of key:fn pairs, run the data through each transformation

  """
  response = {}
  for key,value in data.items():
    response[key] = contract.get(key, lambda x: x)(value)
  return response


def transform_params(**contract):
  """
  Abstract the GET (query params) or POST (json body) + parsing parameters so that
  the underlying view can simply deal with `params` being the pure/pythonified request input

  """
  def outer(func):
    @wraps(func)
    def decorated(*args, **kwargs):
      kwargs['params'] = validate_contract(contract, parameters_from_request())
      return func(*args, **kwargs)
    return decorated
  return outer