jsxn 0.2

Python Metaclass JSON library

jsxn

jsxn is a Python library for JSON objects that use a strict schema. Designed for use with REST APIs that return lists of objects that all have the same attributes.

The jsxn object will pragmatically generate a Python class based on a JSON string, Python dictionary, keyword arguments, or an iterable collection of attribute names.

from jsxn import jsxn

# this will create a jsxn class 'dynamic' that has 'schema' and 'key' as attributes
instance = jsxn.dynamic({'schema':100,'key':'value'})

# str representations of jsxn instances will be JSON
print(instance)
# {"schema": 100, "key": "value"}

# jsxn instances can be passed to dict
print(dict(instance))
# {'schema': 100, 'key': 'value'}

# future references of the class will use the generated class
another = jsxn.dynamic('{"schema":200,"key":"something"}')

# previously generated classes can be called without arguments
builder = jsxn.dynamic()
print(builder)
# {"schema": null, "key": null}

# attributes can be accessed directly
builder.schema = 300
# or by indices
builder['key'] = 'populate'
print(builder)
# {"schema": 300, "key": "populate"}

# jsxn instances are callable with JSON strings
builder('{"schema":500}')
# and keywords
builder(key='hello')
print(builder)
# {"schema": 500, "key": "hello"}

# jsxn objects use slots so only attributes defined at creation can be assigned
try:
    builder.not_defined = True
except AttributeError as e:
    print(e)
    # 'dynamic' object has no attribute 'not_defined'

# delete a jsxn class in order to reuse it
del jsxn.dynamic

# a jsxn class can be defined with a list of keys
instance = jsxn.dynamic(['attr1','attr2','attr3'])
# all the variables will be uninitialized
print(instance)
# {"attr1": null, "attr2": null, "attr3": null}

# jsxn classes can also be deleted by indices
del jsxn['dynamic']

# it is possible to create a jsxn class that accept nothing
empty = jsxn.empty()
print(empty)
# {}
# but it is not very useful...