The RestAPI
Since version 19.5.10 pyDAL includes a restful API [CIT0801] called RestAPI. It is inspired by GraphQL [CIT0802] and while it’s not quite the same due to it being less powerful, it is in the spirit of py4web since it’s more practical and easier to use.
Like GraphQL RestAPI allows a client to query for information using the GET method and allows to specify some details about the format of the response (which references to follow, and how to denormalize the data). Unlike GraphQL it allows the server to specify a policy and restrict which queries are allowed and which ones are not. They can be evaluated dynamically per request based on the user and the state of the server.
As the name implies RestAPI allows all standard methods: GET, POST, PUT, and DELETE. Each of them can be enabled or disabled based on the policy, for individual tables and individual fields.
Note
Specifications might be subject to changes since this is a new feature.
In the examples below we assume a simple app called “superheroes”:
# in superheroes/__init__.py
import os
from py4web import action, request, Field, DAL
from pydal.restapi import RestAPI, Policy
# database definition
DB_FOLDER = os.path.join(os.path.dirname(__file__), 'databases')
if not os.path.isdir(DB_FOLDER):
os.mkdir(DB_FOLDER)
db = DAL('sqlite://storage.sqlite', folder=DB_FOLDER)
db.define_table(
'person',
Field('name'),
Field('job'))
db.define_table(
'superhero',
Field('name'),
Field('real_identity', 'reference person'))
db.define_table(
'superpower',
Field('description'))
db.define_table(
'tag',
Field('superhero', 'reference superhero'),
Field('superpower', 'reference superpower'),
Field('strength', 'integer'))
# add example entries in db
if not db(db.person).count():
db.person.insert(name='Clark Kent', job='Journalist')
db.person.insert(name='Peter Park', job='Photographer')
db.person.insert(name='Bruce Wayne', job='CEO')
db.superhero.insert(name='Superman', real_identity=1)
db.superhero.insert(name='Spiderman', real_identity=2)
db.superhero.insert(name='Batman', real_identity=3)
db.superpower.insert(description='Flight')
db.superpower.insert(description='Strength')
db.superpower.insert(description='Speed')
db.superpower.insert(description='Durability')
db.tag.insert(superhero=1, superpower=1, strength=100)
db.tag.insert(superhero=1, superpower=2, strength=100)
db.tag.insert(superhero=1, superpower=3, strength=100)
db.tag.insert(superhero=1, superpower=4, strength=100)
db.tag.insert(superhero=2, superpower=2, strength=50)
db.tag.insert(superhero=2, superpower=3, strength=75)
db.tag.insert(superhero=2, superpower=4, strength=10)
db.tag.insert(superhero=3, superpower=2, strength=80)
db.tag.insert(superhero=3, superpower=3, strength=20)
db.tag.insert(superhero=3, superpower=4, strength=70)
db.commit()
# policy definitions
policy = Policy()
policy.set('superhero', 'GET', authorize=True, allowed_patterns=['*'])
policy.set('*', 'GET', authorize=True, allowed_patterns=['*'])
# for security reasons we disabled here all methods but GET at the policy level,
# to enable any of them just set authorize = True
policy.set('*', 'PUT', authorize=False)
policy.set('*', 'POST', authorize=False)
policy.set('*', 'DELETE', authorize=False)
@action('api/<tablename>/', method = ['GET', 'POST'])
@action('api/<tablename>/<rec_id>', method = ['GET', 'PUT', 'DELETE'])
@action.uses(db)
def api(tablename, rec_id=None):
return RestAPI(db, policy)(request.method,
tablename,
rec_id,
request.GET,
request.POST
)
@action("index")
def index():
return "RestAPI example"
RestAPI policies and actions
The policy is per table (or * for all tables) and per method. authorize
can be True (allow), False (deny) or a function with the signature
(method, tablename, record_id, get_vars, post_vars) which returns
True/False. For the GET policy one can specify a list of allowed query
patterns (* for all). A query pattern will be matched against the keys
in the query string.
The above action is exposed as:
/superheroes/api/{tablename}
/superheroes/api/{tablename}/{rec_id}
The result can be seen directly with a browser, rendered as JSON.
Let’s look for example at the person table:
The diagram of the superhero’s database should help you interpreting the code:
Note
Keep in mind that request.POST only contains the form data that is posted using a regular HTML-form or JavaScript FormData object.
RestAPI GET
The general query has the form {something}.eq=value where eq=
stands for “equal”, gt= stands for “greater than”, etc. The
expression can be prepended by not..
{something} can be:
the name of a field in the table being queried as in:
All superheroes called “Superman”
/superheroes/api/superhero?name.eq=Superman
the name of a field of a table referred by the table being queried as in:
All superheroes with real identity “Clark Kent”
/superheroes/api/superhero?real_identity.name.eq=Clark Kent
the name of a field of a table that refers to the table being queried as in:
All superheroes with any tag superpower with strength > 90
/superheroes/api/superhero?superhero.tag.strength.gt=90
(here
tagis the name of the link table, the precedingsuperherois the name of the field that refers to the selected table andstrengthis the name of the field used to filter)a field of the table referenced by a many-to-many linked table as in:
All superheroes with the flight power
/superheroes/api/superhero?superhero.tag.superpower.description.eq=Flight
Hint
The key to understand the syntax above is to read it as:
<< select records of table superhero referred by field superhero of table tag, when the superpower field of said table points to a record with description equal to “Flight” >>
The query allows additional modifiers for example:
@offset=10
@limit=10
@order=name
@model=true
@lookup=real_identity
The first 3 are obvious. @model returns a JSON description of database
model. @lookup denormalizes the linked field.
RestAPI practical examples
Here are some practical examples:
URL:
/superheroes/api/superhero
OUTPUT:
{
"count": 3,
"status": "success",
"code": 200,
"items": [
{
"real_identity": 1,
"name": "Superman",
"id": 1
},
{
"real_identity": 2,
"name": "Spiderman",
"id": 2
},
{
"real_identity": 3,
"name": "Batman",
"id": 3
}
],
"timestamp": "2019-05-19T05:38:00.132635",
"api_version": "0.1"
}
URL:
/superheroes/api/superhero?@model=true
OUTPUT:
{
"count": 3,
"status": "success",
"code": 200,
"items": [
{
"real_identity": 1,
"name": "Superman",
"id": 1
},
{
"real_identity": 2,
"name": "Spiderman",
"id": 2
},
{
"real_identity": 3,
"name": "Batman",
"id": 3
}
],
"timestamp": "2021-01-04T07:03:38.466030",
"model": [
{
"regex": "[1-9]\\d*",
"name": "id",
"default": null,
"required": false,
"label": "Id",
"post_writable": true,
"referenced_by": [
"tag.superhero"
],
"unique": false,
"type": "id",
"options": null,
"put_writable": true
},
{
"regex": null,
"name": "name",
"default": null,
"required": false,
"label": "Name",
"post_writable": true,
"unique": false,
"type": "string",
"options": null,
"put_writable": true
},
{
"regex": null,
"name": "real_identity",
"default": null,
"required": false,
"label": "Real Identity",
"post_writable": true,
"references": "person",
"unique": false,
"type": "reference",
"options": null,
"put_writable": true
}
],
"api_version": "0.1"
}
URL:
/superheroes/api/superhero?@lookup=real_identity
OUTPUT:
{
"count": 3,
"status": "success",
"code": 200,
"items": [
{
"real_identity": {
"name": "Clark Kent",
"job": "Journalist",
"id": 1
},
"name": "Superman",
"id": 1
},
{
"real_identity": {
"name": "Peter Park",
"job": "Photographer",
"id": 2
},
"name": "Spiderman",
"id": 2
},
{
"real_identity": {
"name": "Bruce Wayne",
"job": "CEO",
"id": 3
},
"name": "Batman",
"id": 3
}
],
"timestamp": "2019-05-19T05:38:00.178974",
"api_version": "0.1"
}
URL:
/superheroes/api/superhero?@lookup=identity:real_identity
(denormalize the real_identity and rename it identity)
OUTPUT:
{
"count": 3,
"status": "success",
"code": 200,
"items": [
{
"real_identity": 1,
"name": "Superman",
"id": 1,
"identity": {
"name": "Clark Kent",
"job": "Journalist",
"id": 1
}
},
{
"real_identity": 2,
"name": "Spiderman",
"id": 2,
"identity": {
"name": "Peter Park",
"job": "Photographer",
"id": 2
}
},
{
"real_identity": 3,
"name": "Batman",
"id": 3,
"identity": {
"name": "Bruce Wayne",
"job": "CEO",
"id": 3
}
}
],
"timestamp": "2019-05-19T05:38:00.123218",
"api_version": "0.1"
}
URL:
/superheroes/api/superhero?@lookup=identity!:real_identity[name,job]
(denormalize the real_identity [but only fields name and job], collapse the with the identity prefix)
OUTPUT:
{
"count": 3,
"status": "success",
"code": 200,
"items": [
{
"name": "Superman",
"identity.job": "Journalist",
"identity.name": "Clark Kent",
"id": 1
},
{
"name": "Spiderman",
"identity.job": "Photographer",
"identity.name": "Peter Park",
"id": 2
},
{
"name": "Batman",
"identity.job": "CEO",
"identity.name": "Bruce Wayne",
"id": 3
}
],
"timestamp": "2021-01-04T07:03:38.559918",
"api_version": "0.1"
}
URL:
/superheroes/api/superhero?@lookup=superhero.tag
OUTPUT:
{
"count": 3,
"status": "success",
"code": 200,
"items": [
{
"real_identity": 1,
"name": "Superman",
"superhero.tag": [
{
"strength": 100,
"superhero": 1,
"id": 1,
"superpower": 1
},
{
"strength": 100,
"superhero": 1,
"id": 2,
"superpower": 2
},
{
"strength": 100,
"superhero": 1,
"id": 3,
"superpower": 3
},
{
"strength": 100,
"superhero": 1,
"id": 4,
"superpower": 4
}
],
"id": 1
},
{
"real_identity": 2,
"name": "Spiderman",
"superhero.tag": [
{
"strength": 50,
"superhero": 2,
"id": 5,
"superpower": 2
},
{
"strength": 75,
"superhero": 2,
"id": 6,
"superpower": 3
},
{
"strength": 10,
"superhero": 2,
"id": 7,
"superpower": 4
}
],
"id": 2
},
{
"real_identity": 3,
"name": "Batman",
"superhero.tag": [
{
"strength": 80,
"superhero": 3,
"id": 8,
"superpower": 2
},
{
"strength": 20,
"superhero": 3,
"id": 9,
"superpower": 3
},
{
"strength": 70,
"superhero": 3,
"id": 10,
"superpower": 4
}
],
"id": 3
}
],
"timestamp": "2019-05-19T05:38:00.201988",
"api_version": "0.1"
}
URL:
/superheroes/api/superhero?@lookup=superhero.tag.superpower
OUTPUT:
{
"count": 3,
"status": "success",
"code": 200,
"items": [
{
"real_identity": 1,
"name": "Superman",
"superhero.tag.superpower": [
{
"strength": 100,
"superhero": 1,
"id": 1,
"superpower": {
"id": 1,
"description": "Flight"
}
},
{
"strength": 100,
"superhero": 1,
"id": 2,
"superpower": {
"id": 2,
"description": "Strength"
}
},
{
"strength": 100,
"superhero": 1,
"id": 3,
"superpower": {
"id": 3,
"description": "Speed"
}
},
{
"strength": 100,
"superhero": 1,
"id": 4,
"superpower": {
"id": 4,
"description": "Durability"
}
}
],
"id": 1
},
{
"real_identity": 2,
"name": "Spiderman",
"superhero.tag.superpower": [
{
"strength": 50,
"superhero": 2,
"id": 5,
"superpower": {
"id": 2,
"description": "Strength"
}
},
{
"strength": 75,
"superhero": 2,
"id": 6,
"superpower": {
"id": 3,
"description": "Speed"
}
},
{
"strength": 10,
"superhero": 2,
"id": 7,
"superpower": {
"id": 4,
"description": "Durability"
}
}
],
"id": 2
},
{
"real_identity": 3,
"name": "Batman",
"superhero.tag.superpower": [
{
"strength": 80,
"superhero": 3,
"id": 8,
"superpower": {
"id": 2,
"description": "Strength"
}
},
{
"strength": 20,
"superhero": 3,
"id": 9,
"superpower": {
"id": 3,
"description": "Speed"
}
},
{
"strength": 70,
"superhero": 3,
"id": 10,
"superpower": {
"id": 4,
"description": "Durability"
}
}
],
"id": 3
}
],
"timestamp": "2019-05-19T05:38:00.322494",
"api_version": "0.1"
}
URL (it’s a single line, split for readability):
/superheroes/api/superhero?
@lookup=powers:superhero.tag[strength].superpower[description]
OUTPUT:
{
"count": 3,
"status": "success",
"code": 200,
"items": [
{
"real_identity": 1,
"name": "Superman",
"powers": [
{
"strength": 100,
"superpower": {
"description": "Flight"
}
},
{
"strength": 100,
"superpower": {
"description": "Strength"
}
},
{
"strength": 100,
"superpower": {
"description": "Speed"
}
},
{
"strength": 100,
"superpower": {
"description": "Durability"
}
}
],
"id": 1
},
{
"real_identity": 2,
"name": "Spiderman",
"powers": [
{
"strength": 50,
"superpower": {
"description": "Strength"
}
},
{
"strength": 75,
"superpower": {
"description": "Speed"
}
},
{
"strength": 10,
"superpower": {
"description": "Durability"
}
}
],
"id": 2
},
{
"real_identity": 3,
"name": "Batman",
"powers": [
{
"strength": 80,
"superpower": {
"description": "Strength"
}
},
{
"strength": 20,
"superpower": {
"description": "Speed"
}
},
{
"strength": 70,
"superpower": {
"description": "Durability"
}
}
],
"id": 3
}
],
"timestamp": "2019-05-19T05:38:00.309903",
"api_version": "0.1"
}
URL (it’s a single line, split for readability):
/superheroes/api/superhero?
@lookup=powers!:superhero.tag[strength].superpower[description]
OUTPUT:
{
"count": 3,
"status": "success",
"code": 200,
"items": [
{
"real_identity": 1,
"name": "Superman",
"powers": [
{
"strength": 100,
"description": "Flight"
},
{
"strength": 100,
"description": "Strength"
},
{
"strength": 100,
"description": "Speed"
},
{
"strength": 100,
"description": "Durability"
}
],
"id": 1
},
{
"real_identity": 2,
"name": "Spiderman",
"powers": [
{
"strength": 50,
"description": "Strength"
},
{
"strength": 75,
"description": "Speed"
},
{
"strength": 10,
"description": "Durability"
}
],
"id": 2
},
{
"real_identity": 3,
"name": "Batman",
"powers": [
{
"strength": 80,
"description": "Strength"
},
{
"strength": 20,
"description": "Speed"
},
{
"strength": 70,
"description": "Durability"
}
],
"id": 3
}
],
"timestamp": "2019-05-19T05:38:00.355181",
"api_version": "0.1"
}
URL (it’s a single line, split for readability):
/superheroes/api/superhero?
@lookup=powers!:superhero.tag[strength].superpower[description],
identity!:real_identity[name]
OUTPUT:
{
"count": 3,
"status": "success",
"code": 200,
"items": [
{
"name": "Superman",
"identity.name": "Clark Kent",
"powers": [
{
"strength": 100,
"description": "Flight"
},
{
"strength": 100,
"description": "Strength"
},
{
"strength": 100,
"description": "Speed"
},
{
"strength": 100,
"description": "Durability"
}
],
"id": 1
},
{
"name": "Spiderman",
"identity.name": "Peter Park",
"powers": [
{
"strength": 50,
"description": "Strength"
},
{
"strength": 75,
"description": "Speed"
},
{
"strength": 10,
"description": "Durability"
}
],
"id": 2
},
{
"name": "Batman",
"identity.name": "Bruce Wayne",
"powers": [
{
"strength": 80,
"description": "Strength"
},
{
"strength": 20,
"description": "Speed"
},
{
"strength": 70,
"description": "Durability"
}
],
"id": 3
}
],
"timestamp": "2021-01-04T07:31:34.974953",
"api_version": "0.1"
}
URL:
/superheroes/api/superhero?name.eq=Superman
OUTPUT:
{
"count": 1,
"status": "success",
"code": 200,
"items": [
{
"real_identity": 1,
"name": "Superman",
"id": 1
}
],
"timestamp": "2019-05-19T05:38:00.405515",
"api_version": "0.1"
}
URL:
/superheroes/api/superhero?real_identity.name.eq=Clark Kent
OUTPUT:
{
"count": 1,
"status": "success",
"code": 200,
"items": [
{
"real_identity": 1,
"name": "Superman",
"id": 1
}
],
"timestamp": "2019-05-19T05:38:00.366288",
"api_version": "0.1"
}
URL:
/superheroes/api/superhero?not.real_identity.name.eq=Clark Kent
OUTPUT:
{
"count": 2,
"status": "success",
"code": 200,
"items": [
{
"real_identity": 2,
"name": "Spiderman",
"id": 2
},
{
"real_identity": 3,
"name": "Batman",
"id": 3
}
],
"timestamp": "2019-05-19T05:38:00.451907",
"api_version": "0.1"
}
URL:
/superheroes/api/superhero?superhero.tag.superpower.description=Flight
OUTPUT:
{
"count": 1,
"status": "success",
"code": 200,
"items": [
{
"real_identity": 1,
"name": "Superman",
"id": 1
}
],
"timestamp": "2019-05-19T05:38:00.453020",
"api_version": "0.1"
}
The RestAPI response
All RestAPI response have the fields:
- api_version:
RestAPI version.
- timestamp:
Datetime in ISO 8601 format.
- status:
RestAPI status (i.e. “success” or “error”).
- code:
HTTP status.
Other optional fields are:
- count:
Total matching (not total returned), for GET.
- items:
In response to a GET.
- errors:
Usually a validation error.
- models:
Usually if status != “success”.
- message:
For error details.