gistfile1.py

def jsonizable(atoms=(), lists=(), objects=()):
    """Adds a `to_json` method to decorated classes:
    
        >>> @jsonizable(atoms=['name', 'age'])
        ... class Example(object):
        ...     def __init__(self, name, age):
        ...         self.name = name
        ...         self.age = age
        ...
        >>> e = Example('bob', 37)
        >>> e.to_json()
        {'name': 'bob', 'age': 37}
    
    JSON fields containing nested lists or collections must be handled specially:
    
        >>> @jsonizable(atoms=['name'])
        ... class Person(object):
        ...     def __init__(self, name):
        ...         self.name = name
        ... 
        >>> @jsonizable(lists=['students'], objects=['teacher'])
        ... class Classroom(object):
        ...     def __init__(self, students, teacher):
        ...         self.students = students
        ...         self.teacher = teacher
        ... 
        >>> students = [Person('bob'), Person('anne')]
        >>> teacher = Person('clarice')
        >>> classroom = Classroom(students, teacher)
        >>> classroom.to_json()
        {'students': [{'name': 'bob'}, {'name': 'anne'}], 'teacher': {'name': 'clarice'}}
    
    The generated to_json method returns a `dict`, allowing callers to further
    manipulate the JSON data before returning it.
    
    The fields to include in the resulting `dict` are given by the optional
    `atoms`, `lists`, and `objects` keyword arguments. Values from attributes
    named in `atoms` will be included in the dict using the equivalent of 
    `getattr(self, atom_attr)`. Values of attributes named in `lists` will be
    turned into lists using the equivalent of
    `[v.to_json for v in getattr(self, list_attr)]`. Values of attributes named
    in `objects` will be turned into nested JSON values using the equivalent
    of `getattr(self, obj_attr).to_json() if getattr(self, obj_attr) else None`.
    """
    def to_json(self):
        json_data = dict()
        
        for attribute in atoms:
            json_data[attribute] = getattr(self, attribute)
        
        for attribute in lists:
            value = getattr(self, attribute)
            if value is None:
                json_data[attribute] = None
            else:
                json_data[attribute] = [element.to_json() for element in value]
        
        for attribute in objects:
            value = getattr(self, attribute)
            if value is None:
                json_data[attribute] = None
            else:
                json_data[attribute] = value.to_json()
        
        return json_data
    
    def decorator(cls):
        cls.to_json = to_json
        return cls
    return decorator