Examples to explain using Python & Flask to implement RESTful Web API

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Environment installation:

sudo pip install flask

Flask is a Python A microservices framework based on Werkzeug, a WSGI class library.

Flask Advantages:

Written in Python (that can be an advantage);
Simple to use;
Flexible;
Multiple good deployment options;
RESTful request dispatching

RESOURCES

An API service that responds to /articles and /articles/:id:

from flask import Flask, url_for
app = Flask(__name__)

@app.route('/')
def api_root():
 return 'Welcome'

@app.route('/articles')
def api_articles():
 return 'List of ' + url_for('api_articles')

@app.route(&#39;/articles/<articleid>&#39;)
def api_article(articleid):
 return &#39;You are reading &#39; + articleid

if __name__ == &#39;__main__&#39;:
 app.run()

Request:

curl http://127.0.0.1:5000/

Response:

GET /
Welcome

GET /articles
List of /articles

GET /articles/123
You are reading 123

REQUESTS

GET Parameters

##

from flask import request

@app.route('/hello')
def api_hello():
 if 'name' in request.args:
  return 'Hello ' + request.args['name']
 else:
  return 'Hello John Doe'

Request:

GET /hello

Hello John Doe

GET /hello?name=Luis

Hello Luis

Request Methods (HTTP Verbs)

@app.route('/echo', methods = ['GET', 'POST', 'PATCH', 'PUT', 'DELETE'])
def api_echo():
 if request.method == 'GET':
  return "ECHO: GET\n"

 elif request.method == 'POST':
  return "ECHO: POST\n"

 elif request.method == 'PATCH':
  return "ECHO: PACTH\n"

 elif request.method == 'PUT':
  return "ECHO: PUT\n"

 elif request.method == 'DELETE':
  return "ECHO: DELETE"

Request specify request type:

curl -X PATCH http://127.0.0.1:5000/echo

GET /echo
ECHO: GET

POST /ECHO

ECHO: POST

Request Data & Headers

from flask import json

@app.route('/messages', methods = ['POST'])
def api_message():

 if request.headers['Content-Type'] == 'text/plain':
  return "Text Message: " + request.data

 elif request.headers['Content-Type'] == 'application/json':
  return "JSON Message: " + json.dumps(request.json)

 elif request.headers['Content-Type'] == 'application/octet-stream':
  f = open('./binary', 'wb')
  f.write(request.data)
    f.close()
  return "Binary message written!"

 else:
  return "415 Unsupported Media Type ;)"

Request specified content type:

curl -H "Content-type: application/json" \

-X POST http://127.0.0.1:5000/messages -d '{"message":"Hello Data"}'

curl -H "Content-type: application/octet-stream" \

-X POST http://127.0.0.1:5000/messages --data-binary @message.bin

##RESPONSES

##

from flask import Response

@app.route('/hello', methods = ['GET'])
def api_hello():
 data = {
  'hello' : 'world',
  'number' : 3
 }
 js = json.dumps(data)

 resp = Response(js, status=200, mimetype='application/json')
 resp.headers['Link'] = 'http://luisrei.com'

 return resp

View response HTTP headers:

curl -i http://127.0.0.1:5000/hello

Optimize code:

from flask import jsonify

Use

resp = jsonify(data)
resp.status_code = 200

Replace

resp = Response(js, status=200, mimetype='application/json')

Status Codes & Errors

@app.errorhandler(404)
def not_found(error=None):
 message = {
   'status': 404,
   'message': 'Not Found: ' + request.url,
 }
 resp = jsonify(message)
 resp.status_code = 404

 return resp

@app.route(&#39;/users/<userid>&#39;, methods = [&#39;GET&#39;])
def api_users(userid):
 users = {&#39;1&#39;:&#39;john&#39;, &#39;2&#39;:&#39;steve&#39;, &#39;3&#39;:&#39;bill&#39;}
 
 if userid in users:
  return jsonify({userid:users[userid]})
 else:
  return not_found()

Request:

GET /users/2

HTTP/1.0 200 OK

{

"2": "steve"
}

GET /users/4
HTTP/1.0 404 NOT FOUND

{

"status": 404,
"message": "Not Found: http://127.0.0.1 :5000/users/4"
}

AUTHORIZATION

##

from functools import wraps

def check_auth(username, password):
 return username == 'admin' and password == 'secret'

def authenticate():
 message = {'message': "Authenticate."}
 resp = jsonify(message)

 resp.status_code = 401
 resp.headers['WWW-Authenticate'] = 'Basic realm="Example"'

 return resp

def requires_auth(f):
 @wraps(f)
 def decorated(*args, **kwargs):
  auth = request.authorization
  if not auth: 
   return authenticate()

  elif not check_auth(auth.username, auth.password):
   return authenticate()
  return f(*args, **kwargs)

 return decorated

replacing the check_auth function and using the requires_auth decorator:

@app.route('/secrets')

@requires_auth

def api_hello():

return "Shhh this is top secret spy stuff!"

HTTP basic authentication：

curl -v -u "admin:secret" http://127.0.0.1:5000/secrets

##SIMPLE DEBUG & LOGGING

Debug:app.run(debug=True)Logging:

import logging
file_handler = logging.FileHandler('app.log')
app.logger.addHandler(file_handler)
app.logger.setLevel(logging.INFO)

@app.route('/hello', methods = ['GET'])
def api_hello():
 app.logger.info('informing')
 app.logger.warning('warning')
 app.logger.error('screaming bloody murder!')
 
 return "check your logs\n"

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