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Serialize and deserialize JSON documents to Python data structures

Project description

EasyJSONParser, a lightweight library for parsing and validating your JSON models

Build Status

Modern Web frameworks all use ORM systems in order to achieve the server-side actions on the database: for instance, Doctrine for Symfony3 (PHP), Mongoose for MongoDB databases.

ORMs have the ability to read data and convert it into a collections of in-memory objects. They can also take a special object and convert it to the underlying storage format.

Motivation behind this project

While ORM-like systems are pretty common in Web development, they are inexistant for all other purposes. For instance, parsing a configuration file (yeah, that's why I designed this library !) and validating its content, or outputting the configuration in a file.


EasyJSONParser only uses the Python's standard library, especially the json module which serialize and unserialize the source/target data.

EasyJSONParser is built for Python 3.


Get the library from Pypi:

> pip install easyjsonparser

Basic examples

In this section, we will define dummy data structure User which follows the following schema:

    "id": "xxx047AD_",
    "username": "jsonisnice",
    "age": 16,
    "isAdmin": false

EasyJSONParser can extract parse the data string into an object with the following code:

import easyjsonparser as ejp
from easyjsonparser.document import JSONObjectDocument

class User(JSONObjectDocument):
    id = ejp.String()
    username = ejp.String()
    age = ejp.Integer()
    isAdmin = ejp.Boolean()

# In this example, the data string is directly
# written in the code but it can have
# various source such as reading a file...
data_string = """

user = User.loads(data_string)

What if you already have loaded your data into a dictionary ? Then, just use load instead of loads:

user = User.load({
    "id": "xxx047AD_",
    "username": "jsonisnice",
    "age": 16,
    "isAdmin": False

We can get a representation of our user instance by just printing it:

>>> print(user)
<JSON UserInstance: {"id": <JSON Value StringInstance: "xxx047AD_">,
 "username": <JSON Value StringInstance: "jsonisnice">, "age": <JSON
  Value IntegerInstance: 16>, "isAdmin": <JSON Value BoolInstance: False>}>

What if we now want to parse a list of User ?

from easyjsonparser.document import JSONAArrayDocument

class UserList(JSONArrayDocument);
    schema = User()

users = UserList.load([
    { ... },
    { ... }

Document-type objects (ie. the ones that inherit from either JSONObjectDocument or JSONArrayDocument) can be mixed into one another.

They also are a variety of types but but the top-level data structure must always be either a JSONObjectDocument or JSONArrayDocument.

Well, now what if we want to turn it back to a JSON string ? Let's use to_json() !

>>>  user.to_json()
'{"id": "xxx047AD_", "username": "jsonisnice", "age": 16, "isAdmin": False}'


Documents are classes that inherits from either JSONObjectDocument or JSONArrayDocument. They are special kinds of Object and Array because they contain class methods used for parsing the data. They behave like normal Object and Array but have the capacity of being a top-level data structure.

The definition of a JSONArrayDocument is a little bit different than using a regular ejp.Array(): the schema must be defined as a class attribute instead of a constructor argument.

class StringList(JSONArrayDocument):
    schema = String()

Here are the following special methods:

JSONObjectDocument.load(obj=None) (@classmethod)

Creates a JSONObjectDocument with input source obj. If no input is given, then an empty data structure is computed. If an input is given but is not a dictionnary, an exception is raised.

JSONObjectDocument.loads(obj_string) (@classmethod)

Creates a JSONObjectDocument from a string. The data is parsed to a dictionary using json.loads() from Python's standard library. If obj_string does not repressent a valid JSON object, an exception is raised.

JSONArrayDocument.load(*values) (@classmethod)

Creates a JSONArrayDocument from a list of values. values can be a variadic array but it is also possible to pass a single input which must be a list or tuple.

JSONArrayDocument.loads(array_string) (@classmethod)

Creates a JSONArrayDocument from a string. The data is parsed to an array using json.loads() from Python's standard library. If array_string does not represent a valid JSON array, an exception is raised.

Available types


Represents a JSON string.


Represents a JSON integer.

*Warning: boolean and floats are accepted as an input but they will be converted to integers with int(). A warning is raised when a conversion happens.

TODO: add an option to disable/enable this behaviour


Represents a floating-point number. Conversion from integers and boolean work the way as ejp.Integer()


Represents a boolean. Conversion from floating-point numbers and boolean work the way as ejp.Integer()


Represents a null value. Every input that is not None (in Python) or null(as a JSON string) will raise a parsing exception.


Represents a JSON object.

Properties cannot be defined in the constructor: they must be defined as class attributes as follows:

class MyObject(ejp.Object):
    property1 = ejp.String()
    property2 = ejp.Boolean()

Note: remember that you need to use JSONObjectDocument to define a top-level object.


Represents a JSON array. An array must follow a schema which must be passed to the constructor of ejp.Array(). If the schema is invalid, an exception is raised.

class MyObject(ejp.Object):
    array = ejp.Array(schema=String())

Note: remember that you need to use JSONArrayDocument to define a top-level array.


Represents an empty value. Used for optional properties/values: if you want to clear the content of an optional parameter, set its value to ejp.Empty().


This software is distributed under the MIT license

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