The RESTAPI

Since version 19.5.10 pyDAL includes a restful API called RestAPI. It is inspired by GraphQL and while it’s not quite the same due to it being less powerful, it is in the spirit of py4web where 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 one are not. They can be evaluated dynamically per request based on the user and the state of the server. As the name implied 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 an app called “superheroes” and the following model:

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'))

We also assume the following controller:

from py4web import action, request
from .common import db
from pydal.restapi import RestAPI, Policy

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
                               )

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}

Note

Keep in mind that request.POST only contains the form data that is posted using a regular HTML-form or JavaScript FormData object. If you post just plain object (e.g. axios.post('path/to/api', {field:'some'})) you should pass request.json instead of request.POST, since the latter will contain just raw request-body which is string, not JSON. See Bottle documentation about request 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

It can be 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

It can be 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 tag is the name of the link table, the preceding superhero is the name of the field that refers to the selected table and strength is the name of the field used to filter)

It can also be 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

The key to understand the syntax above is to break it as follows:

superhero?superhero.tag.superpower.description.eq=Flight

and 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.

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"
}

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.