Creating an API with just Google App Engine, webapp2 and Python?

Question

Is it possible to create an API using just webapp2 and Python on Google App Engine?

For example, let's my route /post/123 is handled by this RequestHandler:

class ShowPosts(webapp2.RequestHandler):
    def get(self):
        posts = Post.query().fetch()
        # return the post as data (JSON) here as response

When a client makes a restful request to /post/123, it can be returned the data object (instead of a rendered html page).

Is this possible or recommended?

GAEfan · Accepted Answer · 2018-08-28T18:51:27.640

You can build a python list or dict object out of the query, then send it as a JSON object, and send that as the response. Try something like this:

import json

posts     = Post.query()
post_json = []

for post in posts:
    post_dict = {
        'name' : post.name,
        'city' : post.city,
        'state': post.state
    }
    post_json.append( post_dict )

return json.dumps(post_json)

UPDATE: OP asked for example with POST method:

import json

class ShowPosts(webapp2.RequestHandler):
    def get(self):
        posts = Post.query()
        post_json   = []

        for post in posts:
            post_dict = {
                'name' : post.name,
                'city' : post.city,
                'state': post.state
            }

            post_json.append( post_dict )

        return json.dumps(post_json) 

    def post(self):
        posts = Post.query()
        post_json   = []

        for post in posts:
            post_dict = {
                'name' : post.name,
                'city' : post.city,
                'state': post.state
            }

            post_json.append( post_dict )

        post_json.append(
            {
                'posted_name': self.request.get('name'),
                'posted_msg': self.request.get('msg')
            }
        )
        return json.dumps(post_json)

Thank you for this example which demonstrates how to handle GET methods. Another part of the API should be able to handle the other http methods; how would we configure this to handle POST or DELETE methods? — puoygae, Aug 28 '18 at 17:29
Not sure I understand. Handling a POST method is basic. You should read https://webapp2.readthedocs.io/en/latest/guide/request.html I don't want to spend any time doing a student's homework. See updated answer. — GAEfan, Aug 28 '18 at 18:53
One thing to note is that when using webapp2 to handle POST requests with params, we use self.request.get('some_field'), whereas, when our app receives restful post requests, it looks like we access the sent data using self.request.body. — puoygae, Aug 31 '18 at 13:12

score 1 · Answer 2 · answered Aug 25 '18 at 21:08

1

You don't have to return a HTML page. You can return a JSON, or even just a string since it's your code that you are hosting. You can easily send up an URL with your App Engine that can respond to a REST call.

answered Aug 25 '18 at 21:08

Ying Li

2,500
2
13
37

What if we are to POST data? How can we do this? If you are willing, would you offer an example in your answer? – puoygae Aug 25 '18 at 23:20

Creating an API with just Google App Engine, webapp2 and Python?

2 Answers2