Preserves Schema

This is an implementation of Preserves Schema for Python 3.

TODO

meta = load_schema_file(__metaschema_filename).schema module-attribute

TODO

Compiler()

TODO

Source code in preserves/schema.py

def __init__(self):
    self.root = Namespace(())

Definition(*args, **kwargs)

Bases: SchemaObject

TODO

Source code in preserves/schema.py

def __init__(self, *args, **kwargs):
    self._fields = args
    if self.SIMPLE:
        if self.EMPTY:
            if len(args) != 0:
                raise TypeError('%s takes no arguments' % (self._constructor_name(),))
        else:
            if len(args) != 1:
                raise TypeError('%s needs exactly one argument' % (self._constructor_name(),))
            self.value = args[0]
    else:
        i = 0
        for arg in args:
            if i >= len(self.FIELD_NAMES):
                raise TypeError('%s given too many positional arguments' % (self._constructor_name(),))
            setattr(self, self.SAFE_FIELD_NAMES[i], arg)
            i = i + 1
        for (argname, arg) in kwargs.items():
            if hasattr(self, argname):
                raise TypeError('%s given duplicate attribute: %r' % (self._constructor_name, argname))
            if argname not in self.SAFE_FIELD_NAMES:
                raise TypeError('%s given unknown attribute: %r' % (self._constructor_name, argname))
            setattr(self, argname, arg)
            i = i + 1
        if i != len(self.FIELD_NAMES):
            raise TypeError('%s needs argument(s) %r' % (self._constructor_name(), self.FIELD_NAMES))

Enumeration()

Bases: SchemaObject

TODO

Source code in preserves/schema.py

def __init__(self):
    raise TypeError('Cannot create instance of Enumeration')

Namespace(prefix)

TODO

Source code in preserves/schema.py

def __init__(self, prefix):
    self._prefix = prefix

SchemaDecodeFailed(cls, p, v, failures=None)

Bases: ValueError

TODO

Source code in preserves/schema.py

def __init__(self, cls, p, v, failures=None):
    super().__init__()
    self.cls = cls
    self.pattern = p
    self.value = v
    self.failures = [] if failures is None else failures

SchemaObject

TODO

__preserve__()

TODO

Source code in preserves/schema.py

def __preserve__(self):
    """TODO"""
    raise NotImplementedError('Subclass responsibility')

decode(v) classmethod

TODO

Source code in preserves/schema.py

@classmethod
def decode(cls, v):
    """TODO"""
    raise NotImplementedError('Subclass responsibility')

try_decode(v) classmethod

TODO

Source code in preserves/schema.py

@classmethod
def try_decode(cls, v):
    """TODO"""
    try:
        return cls.decode(v)
    except SchemaDecodeFailed:
        return None

encode(p, v)

TODO

Source code in preserves/schema.py

def encode(p, v):
    """TODO"""
    if hasattr(v, '__escape_schema__'):
        return preserve(v.__escape_schema__())
    if p == ANY:
        return v
    if p.key == NAMED:
        return encode(p[1], safegetattr(v, p[0].name))
    if p.key == ATOM:
        return v
    if p.key == EMBEDDED:
        return Embedded(v)
    if p.key == LIT:
        return p[0]
    if p.key == SEQOF:
        return tuple(encode(p[0], w) for w in v)
    if p.key == SETOF:
        return set(encode(p[0], w) for w in v)
    if p.key == DICTOF:
        return dict((encode(p[0], k), encode(p[1], w)) for (k, w) in v.items())
    if p.key == REF:
        return preserve(v)
    if p.key == REC:
        return Record(encode(p[0], v), encode(p[1], v))
    if p.key == TUPLE:
        return tuple(encode(pp, v) for pp in p[0])
    if p.key == TUPLE_PREFIX:
        return tuple(encode(pp, v) for pp in p[0]) + encode(p[1], v)
    if p.key == DICT:
        return dict((k, encode(pp, v)) for (k, pp) in p[0].items())
    if p.key == AND:
        return merge(*[encode(pp, v) for pp in p[0]])
    raise ValueError(f'Bad schema {p}')

extend(cls)

TODO

Source code in preserves/schema.py

def extend(cls):
    """TODO"""
    def extender(f):
        setattr(cls, f.__name__, f)
        return f
    return extender

load_schema_file(filename)

TODO

Source code in preserves/schema.py

def load_schema_file(filename):
    """TODO"""
    c = Compiler()
    c.load(filename)
    return c.root

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Last update: March 16, 2023
Created: March 16, 2023