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Basic RESTFul API Server With Python Flask

A Basic RESTFul API Service with Python Flask. We will be using the Flask, jsonify and request classes to build our API service.

Description of this demonstration:

Our API will be able to do the following:

  • Create, Read, Update, Delete

In this demonstration, we will add some information about people to our API, then go through each method that is mentioned above.

Getting the Dependencies:

Setup the virtualenv and install the dependencies:

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$ virtualenv .venv
$ source .venv/bin/activate
$ pip install flask

The API Server Code:

Here’s the complete code, as you can see I have a couple of decorators for each url endpoint, and a id_generator function, that will generate id’s for each document. The id will be used for getting users information, updates and deletes:

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from flask import Flask, jsonify, request
from multiprocessing import Value

counter = Value('i', 0)
app = Flask(__name__)

a = []
help_message = """
API Usage:
 
- GET    /api/list
- POST   /api/add data={"key": "value"}
- GET    /api/get/<id>
- PUT    /api/update/<id> data={"key": "value_to_replace"}
- DELETE /api/delete/<id> 

"""

def id_generator():
    with counter.get_lock():
        counter.value += 1
        return counter.value

@app.route('/api', methods=['GET'])
def help():
    return help_message

@app.route('/api/list', methods=['GET'])
def list():
    return jsonify(a)

@app.route('/api/add', methods=['POST'])
def index():
    payload = request.json
    payload['id'] = id_generator()
    a.append(payload)
    return "Created: {} \n".format(payload)

@app.route('/api/get', methods=['GET'])
def get_none():
    return 'ID Required: /api/get/<id> \n'

@app.route('/api/get/<int:_id>', methods=['GET'])
def get(_id):
    for user in a:
        if _id == user['id']:
            selected_user = user
    return jsonify(selected_user)

@app.route('/api/update', methods=['PUT'])
def update_none():
    return 'ID and Desired K/V in Payload required: /api/update/<id> -d \'{"name": "john"}\' \n'

@app.route('/api/update/<int:_id>', methods=['PUT'])
def update(_id):
    update_req = request.json
    key_to_update = update_req.keys()[0]
    update_val = (item for item in a if item['id'] == _id).next()[key_to_update] = update_req.values()[0]
    update_resp = (item for item in a if item['id'] == _id).next()
    return "Updated: {} \n".format(update_resp)

@app.route('/api/delete/<int:_id>', methods=['DELETE'])
def delete(_id):
    deleted_user = (item for item in a if item['id'] == _id).next()
    a.remove(deleted_user)
    return "Deleted: {} \n".format(deleted_user)

if __name__ == '__main__':
    app.run()

Demo Time:

Retrieving the Help output:

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$ curl -XGET -H 'Content-Type: application/json' http://localhost:5000/api

API Usage:

- GET    /api/list
- POST   /api/add data={"key": "value"}
- GET    /api/get/<id>
- PUT    /api/update/<id> data={"key": "value_to_replace"}
- DELETE /api/delete/<id>

Doing a list, to list all the users, its expected for it to be empty as we have not added any info to our API:

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$ curl -XGET -H 'Content-Type: application/json' http://localhost:5000/api/list
[]

Adding our first user:

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$ curl -XPOST -H 'Content-Type: application/json' http://localhost:5000/api/add -d '{"name": "ruan", "country": "south africa", "age": 30}'
Created: {u'country': u'south africa', u'age': 30, u'name': u'ruan', 'id': 1}

Adding our second user:

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$ curl -XPOST -H 'Content-Type: application/json' http://localhost:5000/api/add -d '{"name": "stefan", "country": "south africa", "age": 29}'
Created: {u'country': u'south africa', u'age': 29, u'name': u'stefan', 'id': 2}

Doing a list again, will retrieve all our users:

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$ curl -XGET -H 'Content-Type: application/json' http://localhost:5000/api/list
[
  {
    "age": 30,
    "country": "south africa",
    "id": 1,
    "name": "ruan"
  },
  {
    "age": 29,
    "country": "south africa",
    "id": 2,
    "name": "stefan"
  }
]

Doing a GET on the userid, to only display the users info:

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$ curl -XGET -H 'Content-Type: application/json' http://localhost:5000/api/get/2
{
  "age": 29,
  "country": "south africa",
  "id": 2,
  "name": "stefan"
}

Now, let’s update some details. Let’s say that Stefan relocated to New Zealand. We will need to provide his id and also the key/value that we want to update:

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$ curl -XPUT -H 'Content-Type: application/json' http://localhost:5000/api/update/2 -d '{"country": "new zealand"}'
Updated: {u'country': u'new zealand', u'age': 29, u'name': u'stefan', 'id': 2}

As you can see the response confirmed that the value was updated, but let’s verify the output, by doing a get on his id:

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$ curl -XGET -H 'Content-Type: application/json' http://localhost:5000/api/get/2
{
  "age": 29,
  "country": "new zealand",
  "id": 2,
  "name": "stefan"
}

And lastly, lets delete our user, which will only require the userid:

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$ curl -XDELETE -H 'Content-Type: application/json' http://localhost:5000/api/delete/2
Deleted: {u'country': u'new zealand', u'age': 29, u'name': u'stefan', 'id': 2}

To verify this, list all the users:

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$ curl -XGET -H 'Content-Type: application/json' http://localhost:5000/api/list
[
  {
    "age": 30,
    "country": "south africa",
    "id": 1,
    "name": "ruan"
  }
]

Using Python Requests:

We can also use python’s requests module to do the same, to give a demonstration I will create a new user:

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$ pip install requests
$ python
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>>> import requests
>>> import json

>>> base_url = 'http://localhost:5000/api/add'
>>> headers = {"Content-Type": "application/json"}
>>> payload = json.dumps({"name": "shaun", "country": "australia", "age": 24})

>>> r = requests.post(base_url, headers=headers, data=payload)
>>> r.content
Created: {u'country': u'australia', u'age': 24, u'name': u'shaun', 'id': 4}

Thats it. I’ve stumbled upon Flask-Restful which I still want to check out, and as soon as I do, I will do a post on it, maybe baked with a NoSQL db or something like that.

Cheers!

Resources:

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