1040 lines
39 KiB
Python
1040 lines
39 KiB
Python
import sys
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import copy
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import types
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import inspect
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__all__ = ['dataclass',
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'field',
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'Field',
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'FrozenInstanceError',
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'InitVar',
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'MISSING',
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# Helper functions.
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'fields',
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'asdict',
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'astuple',
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'make_dataclass',
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'replace',
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'is_dataclass',
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]
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# Conditions for adding methods. The boxes indicate what action the
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# dataclass decorator takes. For all of these tables, when I talk
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# about init=, repr=, eq=, order=, unsafe_hash=, or frozen=, I'm
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# referring to the arguments to the @dataclass decorator. When
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# checking if a dunder method already exists, I mean check for an
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# entry in the class's __dict__. I never check to see if an
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# attribute is defined in a base class.
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# Key:
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# +=========+=========================================+
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# + Value | Meaning |
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# +=========+=========================================+
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# | <blank> | No action: no method is added. |
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# +---------+-----------------------------------------+
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# | add | Generated method is added. |
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# +---------+-----------------------------------------+
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# | raise | TypeError is raised. |
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# +---------+-----------------------------------------+
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# | None | Attribute is set to None. |
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# +=========+=========================================+
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# __init__
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#
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# +--- init= parameter
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# |
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# v | | |
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# | no | yes | <--- class has __init__ in __dict__?
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# +=======+=======+=======+
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# | False | | |
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# +-------+-------+-------+
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# | True | add | | <- the default
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# +=======+=======+=======+
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# __repr__
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#
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# +--- repr= parameter
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# |
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# v | | |
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# | no | yes | <--- class has __repr__ in __dict__?
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# +=======+=======+=======+
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# | False | | |
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# +-------+-------+-------+
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# | True | add | | <- the default
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# +=======+=======+=======+
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# __setattr__
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# __delattr__
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#
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# +--- frozen= parameter
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# |
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# v | | |
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# | no | yes | <--- class has __setattr__ or __delattr__ in __dict__?
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# +=======+=======+=======+
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# | False | | | <- the default
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# +-------+-------+-------+
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# | True | add | raise |
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# +=======+=======+=======+
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# Raise because not adding these methods would break the "frozen-ness"
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# of the class.
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# __eq__
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#
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# +--- eq= parameter
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# |
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# v | | |
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# | no | yes | <--- class has __eq__ in __dict__?
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# +=======+=======+=======+
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# | False | | |
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# +-------+-------+-------+
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# | True | add | | <- the default
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# +=======+=======+=======+
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# __lt__
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# __le__
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# __gt__
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# __ge__
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#
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# +--- order= parameter
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# |
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# v | | |
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# | no | yes | <--- class has any comparison method in __dict__?
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# +=======+=======+=======+
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# | False | | | <- the default
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# +-------+-------+-------+
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# | True | add | raise |
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# +=======+=======+=======+
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# Raise because to allow this case would interfere with using
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# functools.total_ordering.
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# __hash__
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# +------------------- unsafe_hash= parameter
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# | +----------- eq= parameter
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# | | +--- frozen= parameter
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# | | |
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# v v v | | |
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# | no | yes | <--- class has explicitly defined __hash__
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# +=======+=======+=======+========+========+
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# | False | False | False | | | No __eq__, use the base class __hash__
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# +-------+-------+-------+--------+--------+
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# | False | False | True | | | No __eq__, use the base class __hash__
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# +-------+-------+-------+--------+--------+
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# | False | True | False | None | | <-- the default, not hashable
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# +-------+-------+-------+--------+--------+
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# | False | True | True | add | | Frozen, so hashable, allows override
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# +-------+-------+-------+--------+--------+
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# | True | False | False | add | raise | Has no __eq__, but hashable
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# +-------+-------+-------+--------+--------+
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# | True | False | True | add | raise | Has no __eq__, but hashable
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# +-------+-------+-------+--------+--------+
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# | True | True | False | add | raise | Not frozen, but hashable
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# +-------+-------+-------+--------+--------+
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# | True | True | True | add | raise | Frozen, so hashable
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# +=======+=======+=======+========+========+
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# For boxes that are blank, __hash__ is untouched and therefore
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# inherited from the base class. If the base is object, then
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# id-based hashing is used.
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# Note that a class may already have __hash__=None if it specified an
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# __eq__ method in the class body (not one that was created by
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# @dataclass).
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# See _hash_action (below) for a coded version of this table.
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# Raised when an attempt is made to modify a frozen class.
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class FrozenInstanceError(AttributeError): pass
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# A sentinel object for default values to signal that a
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# default factory will be used.
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# This is given a nice repr() which will appear in the function
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# signature of dataclasses' constructors.
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class _HAS_DEFAULT_FACTORY_CLASS:
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def __repr__(self):
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return '<factory>'
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_HAS_DEFAULT_FACTORY = _HAS_DEFAULT_FACTORY_CLASS()
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# A sentinel object to detect if a parameter is supplied or not. Use
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# a class to give it a better repr.
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class _MISSING_TYPE:
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pass
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MISSING = _MISSING_TYPE()
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# Since most per-field metadata will be unused, create an empty
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# read-only proxy that can be shared among all fields.
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_EMPTY_METADATA = types.MappingProxyType({})
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# Markers for the various kinds of fields and pseudo-fields.
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_FIELD = object() # An actual field.
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_FIELD_CLASSVAR = object() # Not a field, but a ClassVar.
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_FIELD_INITVAR = object() # Not a field, but an InitVar.
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# The name of an attribute on the class where we store the Field
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# objects. Also used to check if a class is a Data Class.
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_FIELDS = '__dataclass_fields__'
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# The name of an attribute on the class that stores the parameters to
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# @dataclass.
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_PARAMS = '__dataclass_params__'
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# The name of the function, that if it exists, is called at the end of
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# __init__.
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_POST_INIT_NAME = '__post_init__'
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class _InitVarMeta(type):
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def __getitem__(self, params):
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return self
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class InitVar(metaclass=_InitVarMeta):
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pass
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# Instances of Field are only ever created from within this module,
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# and only from the field() function, although Field instances are
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# exposed externally as (conceptually) read-only objects.
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# name and type are filled in after the fact, not in __init__. They're
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# not known at the time this class is instantiated, but it's
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# convenient if they're available later.
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# When cls._FIELDS is filled in with a list of Field objects, the name
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# and type fields will have been populated.
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class Field:
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__slots__ = ('name',
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'type',
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'default',
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'default_factory',
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'repr',
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'hash',
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'init',
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'compare',
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'metadata',
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'_field_type', # Private: not to be used by user code.
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)
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def __init__(self, default, default_factory, init, repr, hash, compare,
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metadata):
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self.name = None
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self.type = None
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self.default = default
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self.default_factory = default_factory
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self.init = init
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self.repr = repr
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self.hash = hash
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self.compare = compare
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self.metadata = (_EMPTY_METADATA
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if metadata is None or len(metadata) == 0 else
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types.MappingProxyType(metadata))
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self._field_type = None
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def __repr__(self):
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return ('Field('
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f'name={self.name!r},'
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f'type={self.type},'
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f'default={self.default},'
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f'default_factory={self.default_factory},'
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f'init={self.init},'
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f'repr={self.repr},'
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f'hash={self.hash},'
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f'compare={self.compare},'
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f'metadata={self.metadata}'
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')')
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class _DataclassParams:
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__slots__ = ('init',
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'repr',
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'eq',
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'order',
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'unsafe_hash',
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'frozen',
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)
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def __init__(self, init, repr, eq, order, unsafe_hash, frozen):
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self.init = init
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self.repr = repr
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self.eq = eq
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self.order = order
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self.unsafe_hash = unsafe_hash
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self.frozen = frozen
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def __repr__(self):
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return ('_DataclassParams('
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f'init={self.init},'
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f'repr={self.repr},'
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f'eq={self.eq},'
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f'order={self.order},'
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f'unsafe_hash={self.unsafe_hash},'
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f'frozen={self.frozen}'
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')')
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# This function is used instead of exposing Field creation directly,
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# so that a type checker can be told (via overloads) that this is a
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# function whose type depends on its parameters.
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def field(*, default=MISSING, default_factory=MISSING, init=True, repr=True,
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hash=None, compare=True, metadata=None):
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"""Return an object to identify dataclass fields.
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default is the default value of the field. default_factory is a
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0-argument function called to initialize a field's value. If init
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is True, the field will be a parameter to the class's __init__()
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function. If repr is True, the field will be included in the
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object's repr(). If hash is True, the field will be included in
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the object's hash(). If compare is True, the field will be used in
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comparison functions. metadata, if specified, must be a mapping
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which is stored but not otherwise examined by dataclass.
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It is an error to specify both default and default_factory.
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"""
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if default is not MISSING and default_factory is not MISSING:
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raise ValueError('cannot specify both default and default_factory')
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return Field(default, default_factory, init, repr, hash, compare,
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metadata)
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def _tuple_str(obj_name, fields):
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# Return a string representing each field of obj_name as a tuple
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# member. So, if fields is ['x', 'y'] and obj_name is "self",
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# return "(self.x,self.y)".
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# Special case for the 0-tuple.
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if not fields:
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return '()'
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# Note the trailing comma, needed if this turns out to be a 1-tuple.
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return f'({",".join([f"{obj_name}.{f.name}" for f in fields])},)'
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def _create_fn(name, args, body, *, globals=None, locals=None,
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return_type=MISSING):
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# Note that we mutate locals when exec() is called. Caller beware!
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# The only callers are internal to this module, so no worries
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# about external callers.
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if locals is None:
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locals = {}
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return_annotation = ''
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if return_type is not MISSING:
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locals['_return_type'] = return_type
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return_annotation = '->_return_type'
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args = ','.join(args)
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body = '\n'.join(f' {b}' for b in body)
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# Compute the text of the entire function.
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txt = f'def {name}({args}){return_annotation}:\n{body}'
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exec(txt, globals, locals)
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return locals[name]
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def _field_assign(frozen, name, value, self_name):
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# If we're a frozen class, then assign to our fields in __init__
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# via object.__setattr__. Otherwise, just use a simple
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# assignment.
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# self_name is what "self" is called in this function: don't
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# hard-code "self", since that might be a field name.
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if frozen:
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return f'object.__setattr__({self_name},{name!r},{value})'
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return f'{self_name}.{name}={value}'
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def _field_init(f, frozen, globals, self_name):
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# Return the text of the line in the body of __init__ that will
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# initialize this field.
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default_name = f'_dflt_{f.name}'
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if f.default_factory is not MISSING:
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if f.init:
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# This field has a default factory. If a parameter is
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# given, use it. If not, call the factory.
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globals[default_name] = f.default_factory
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value = (f'{default_name}() '
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f'if {f.name} is _HAS_DEFAULT_FACTORY '
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f'else {f.name}')
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else:
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# This is a field that's not in the __init__ params, but
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# has a default factory function. It needs to be
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# initialized here by calling the factory function,
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# because there's no other way to initialize it.
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# For a field initialized with a default=defaultvalue, the
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# class dict just has the default value
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# (cls.fieldname=defaultvalue). But that won't work for a
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# default factory, the factory must be called in __init__
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# and we must assign that to self.fieldname. We can't
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# fall back to the class dict's value, both because it's
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# not set, and because it might be different per-class
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# (which, after all, is why we have a factory function!).
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globals[default_name] = f.default_factory
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value = f'{default_name}()'
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else:
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# No default factory.
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if f.init:
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if f.default is MISSING:
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# There's no default, just do an assignment.
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value = f.name
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elif f.default is not MISSING:
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globals[default_name] = f.default
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value = f.name
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else:
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# This field does not need initialization. Signify that to
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# the caller by returning None.
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return None
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# Only test this now, so that we can create variables for the
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# default. However, return None to signify that we're not going
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# to actually do the assignment statement for InitVars.
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if f._field_type == _FIELD_INITVAR:
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return None
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# Now, actually generate the field assignment.
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return _field_assign(frozen, f.name, value, self_name)
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def _init_param(f):
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# Return the __init__ parameter string for this field.
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# For example, the equivalent of 'x:int=3' (except instead of 'int',
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# reference a variable set to int, and instead of '3', reference a
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# variable set to 3).
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if f.default is MISSING and f.default_factory is MISSING:
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# There's no default, and no default_factory, just
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# output the variable name and type.
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default = ''
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elif f.default is not MISSING:
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# There's a default, this will be the name that's used to look it up.
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default = f'=_dflt_{f.name}'
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elif f.default_factory is not MISSING:
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# There's a factory function. Set a marker.
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default = '=_HAS_DEFAULT_FACTORY'
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return f'{f.name}:_type_{f.name}{default}'
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def _init_fn(fields, frozen, has_post_init, self_name):
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# fields contains both real fields and InitVar pseudo-fields.
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# Make sure we don't have fields without defaults following fields
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# with defaults. This actually would be caught when exec-ing the
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# function source code, but catching it here gives a better error
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# message, and future-proofs us in case we build up the function
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# using ast.
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seen_default = False
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for f in fields:
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# Only consider fields in the __init__ call.
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if f.init:
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if not (f.default is MISSING and f.default_factory is MISSING):
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seen_default = True
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elif seen_default:
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raise TypeError(f'non-default argument {f.name!r} '
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'follows default argument')
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globals = {'MISSING': MISSING,
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'_HAS_DEFAULT_FACTORY': _HAS_DEFAULT_FACTORY}
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body_lines = []
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for f in fields:
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line = _field_init(f, frozen, globals, self_name)
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# line is None means that this field doesn't require
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# initialization (it's a pseudo-field). Just skip it.
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if line:
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body_lines.append(line)
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# Does this class have a post-init function?
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if has_post_init:
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params_str = ','.join(f.name for f in fields
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if f._field_type is _FIELD_INITVAR)
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body_lines.append(f'{self_name}.{_POST_INIT_NAME}({params_str})')
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# If no body lines, use 'pass'.
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if not body_lines:
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body_lines = ['pass']
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locals = {f'_type_{f.name}': f.type for f in fields}
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return _create_fn('__init__',
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[self_name] + [_init_param(f) for f in fields if f.init],
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body_lines,
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locals=locals,
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globals=globals,
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return_type=None)
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|
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def _repr_fn(fields):
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return _create_fn('__repr__',
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('self',),
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['return self.__class__.__qualname__ + f"(' +
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', '.join([f"{f.name}={{self.{f.name}!r}}"
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for f in fields]) +
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')"'])
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def _frozen_get_del_attr(cls, fields):
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# XXX: globals is modified on the first call to _create_fn, then the
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# modified version is used in the second call. Is this okay?
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globals = {'cls': cls,
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'FrozenInstanceError': FrozenInstanceError}
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if fields:
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fields_str = '(' + ','.join(repr(f.name) for f in fields) + ',)'
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else:
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# Special case for the zero-length tuple.
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fields_str = '()'
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return (_create_fn('__setattr__',
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('self', 'name', 'value'),
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(f'if type(self) is cls or name in {fields_str}:',
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' raise FrozenInstanceError(f"cannot assign to field {name!r}")',
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f'super(cls, self).__setattr__(name, value)'),
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globals=globals),
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_create_fn('__delattr__',
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('self', 'name'),
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(f'if type(self) is cls or name in {fields_str}:',
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' raise FrozenInstanceError(f"cannot delete field {name!r}")',
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f'super(cls, self).__delattr__(name)'),
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globals=globals),
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)
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|
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def _cmp_fn(name, op, self_tuple, other_tuple):
|
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# Create a comparison function. If the fields in the object are
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|
# named 'x' and 'y', then self_tuple is the string
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# '(self.x,self.y)' and other_tuple is the string
|
|
# '(other.x,other.y)'.
|
|
|
|
return _create_fn(name,
|
|
('self', 'other'),
|
|
[ 'if other.__class__ is self.__class__:',
|
|
f' return {self_tuple}{op}{other_tuple}',
|
|
'return NotImplemented'])
|
|
|
|
|
|
def _hash_fn(fields):
|
|
self_tuple = _tuple_str('self', fields)
|
|
return _create_fn('__hash__',
|
|
('self',),
|
|
[f'return hash({self_tuple})'])
|
|
|
|
|
|
def _get_field(cls, a_name, a_type):
|
|
# Return a Field object for this field name and type. ClassVars
|
|
# and InitVars are also returned, but marked as such (see
|
|
# f._field_type).
|
|
|
|
# If the default value isn't derived from Field, then it's
|
|
# only a normal default value. Convert it to a Field().
|
|
default = getattr(cls, a_name, MISSING)
|
|
if isinstance(default, Field):
|
|
f = default
|
|
else:
|
|
if isinstance(default, types.MemberDescriptorType):
|
|
# This is a field in __slots__, so it has no default value.
|
|
default = MISSING
|
|
f = field(default=default)
|
|
|
|
# Assume it's a normal field until proven otherwise.
|
|
f._field_type = _FIELD
|
|
|
|
# Only at this point do we know the name and the type. Set them.
|
|
f.name = a_name
|
|
f.type = a_type
|
|
|
|
# If typing has not been imported, then it's impossible for
|
|
# any annotation to be a ClassVar. So, only look for ClassVar
|
|
# if typing has been imported.
|
|
typing = sys.modules.get('typing')
|
|
if typing is not None:
|
|
# This test uses a typing internal class, but it's the best
|
|
# way to test if this is a ClassVar.
|
|
if (type(a_type) is typing._GenericAlias and
|
|
a_type.__origin__ is typing.ClassVar):
|
|
# This field is a ClassVar, so it's not a field.
|
|
f._field_type = _FIELD_CLASSVAR
|
|
|
|
if f._field_type is _FIELD:
|
|
# Check if this is an InitVar.
|
|
if a_type is InitVar:
|
|
# InitVars are not fields, either.
|
|
f._field_type = _FIELD_INITVAR
|
|
|
|
# Validations for fields. This is delayed until now, instead of
|
|
# in the Field() constructor, since only here do we know the field
|
|
# name, which allows better error reporting.
|
|
|
|
# Special restrictions for ClassVar and InitVar.
|
|
if f._field_type in (_FIELD_CLASSVAR, _FIELD_INITVAR):
|
|
if f.default_factory is not MISSING:
|
|
raise TypeError(f'field {f.name} cannot have a '
|
|
'default factory')
|
|
# Should I check for other field settings? default_factory
|
|
# seems the most serious to check for. Maybe add others.
|
|
# For example, how about init=False (or really,
|
|
# init=<not-the-default-init-value>)? It makes no sense for
|
|
# ClassVar and InitVar to specify init=<anything>.
|
|
|
|
# For real fields, disallow mutable defaults for known types.
|
|
if f._field_type is _FIELD and isinstance(f.default, (list, dict, set)):
|
|
raise ValueError(f'mutable default {type(f.default)} for field '
|
|
f'{f.name} is not allowed: use default_factory')
|
|
|
|
return f
|
|
|
|
|
|
def _set_new_attribute(cls, name, value):
|
|
# Never overwrites an existing attribute. Returns True if the
|
|
# attribute already exists.
|
|
if name in cls.__dict__:
|
|
return True
|
|
setattr(cls, name, value)
|
|
return False
|
|
|
|
|
|
|
|
# Decide if/how we're going to create a hash function. Key is
|
|
# (unsafe_hash, eq, frozen, does-hash-exist). Value is the action to
|
|
# take. The common case is to do nothing, so instead of providing a
|
|
# function that is a no-op, use None to signify that.
|
|
|
|
def _hash_set_none(cls, fields):
|
|
return None
|
|
|
|
def _hash_add(cls, fields):
|
|
flds = [f for f in fields if (f.compare if f.hash is None else f.hash)]
|
|
return _hash_fn(flds)
|
|
|
|
def _hash_exception(cls, fields):
|
|
# Raise an exception.
|
|
raise TypeError(f'Cannot overwrite attribute __hash__ '
|
|
f'in class {cls.__name__}')
|
|
|
|
#
|
|
# +-------------------------------------- unsafe_hash?
|
|
# | +------------------------------- eq?
|
|
# | | +------------------------ frozen?
|
|
# | | | +---------------- has-explicit-hash?
|
|
# | | | |
|
|
# | | | | +------- action
|
|
# | | | | |
|
|
# v v v v v
|
|
_hash_action = {(False, False, False, False): None,
|
|
(False, False, False, True ): None,
|
|
(False, False, True, False): None,
|
|
(False, False, True, True ): None,
|
|
(False, True, False, False): _hash_set_none,
|
|
(False, True, False, True ): None,
|
|
(False, True, True, False): _hash_add,
|
|
(False, True, True, True ): None,
|
|
(True, False, False, False): _hash_add,
|
|
(True, False, False, True ): _hash_exception,
|
|
(True, False, True, False): _hash_add,
|
|
(True, False, True, True ): _hash_exception,
|
|
(True, True, False, False): _hash_add,
|
|
(True, True, False, True ): _hash_exception,
|
|
(True, True, True, False): _hash_add,
|
|
(True, True, True, True ): _hash_exception,
|
|
}
|
|
# See https://bugs.python.org/issue32929#msg312829 for an if-statement
|
|
# version of this table.
|
|
|
|
|
|
def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen):
|
|
# Now that dicts retain insertion order, there's no reason to use
|
|
# an ordered dict. I am leveraging that ordering here, because
|
|
# derived class fields overwrite base class fields, but the order
|
|
# is defined by the base class, which is found first.
|
|
fields = {}
|
|
|
|
setattr(cls, _PARAMS, _DataclassParams(init, repr, eq, order,
|
|
unsafe_hash, frozen))
|
|
|
|
# Find our base classes in reverse MRO order, and exclude
|
|
# ourselves. In reversed order so that more derived classes
|
|
# override earlier field definitions in base classes.
|
|
# As long as we're iterating over them, see if any are frozen.
|
|
any_frozen_base = False
|
|
has_dataclass_bases = False
|
|
for b in cls.__mro__[-1:0:-1]:
|
|
# Only process classes that have been processed by our
|
|
# decorator. That is, they have a _FIELDS attribute.
|
|
base_fields = getattr(b, _FIELDS, None)
|
|
if base_fields:
|
|
has_dataclass_bases = True
|
|
for f in base_fields.values():
|
|
fields[f.name] = f
|
|
if getattr(b, _PARAMS).frozen:
|
|
any_frozen_base = True
|
|
|
|
# Annotations that are defined in this class (not in base
|
|
# classes). If __annotations__ isn't present, then this class
|
|
# adds no new annotations. We use this to compute fields that
|
|
# are added by this class.
|
|
# Fields are found from cls_annotations, which is guaranteed to be
|
|
# ordered. Default values are from class attributes, if a field
|
|
# has a default. If the default value is a Field(), then it
|
|
# contains additional info beyond (and possibly including) the
|
|
# actual default value. Pseudo-fields ClassVars and InitVars are
|
|
# included, despite the fact that they're not real fields.
|
|
# That's dealt with later.
|
|
cls_annotations = cls.__dict__.get('__annotations__', {})
|
|
|
|
# Now find fields in our class. While doing so, validate some
|
|
# things, and set the default values (as class attributes)
|
|
# where we can.
|
|
cls_fields = [_get_field(cls, name, type)
|
|
for name, type in cls_annotations.items()]
|
|
for f in cls_fields:
|
|
fields[f.name] = f
|
|
|
|
# If the class attribute (which is the default value for
|
|
# this field) exists and is of type 'Field', replace it
|
|
# with the real default. This is so that normal class
|
|
# introspection sees a real default value, not a Field.
|
|
if isinstance(getattr(cls, f.name, None), Field):
|
|
if f.default is MISSING:
|
|
# If there's no default, delete the class attribute.
|
|
# This happens if we specify field(repr=False), for
|
|
# example (that is, we specified a field object, but
|
|
# no default value). Also if we're using a default
|
|
# factory. The class attribute should not be set at
|
|
# all in the post-processed class.
|
|
delattr(cls, f.name)
|
|
else:
|
|
setattr(cls, f.name, f.default)
|
|
|
|
# Do we have any Field members that don't also have annotations?
|
|
for name, value in cls.__dict__.items():
|
|
if isinstance(value, Field) and not name in cls_annotations:
|
|
raise TypeError(f'{name!r} is a field but has no type annotation')
|
|
|
|
# Check rules that apply if we are derived from any dataclasses.
|
|
if has_dataclass_bases:
|
|
# Raise an exception if any of our bases are frozen, but we're not.
|
|
if any_frozen_base and not frozen:
|
|
raise TypeError('cannot inherit non-frozen dataclass from a '
|
|
'frozen one')
|
|
|
|
# Raise an exception if we're frozen, but none of our bases are.
|
|
if not any_frozen_base and frozen:
|
|
raise TypeError('cannot inherit frozen dataclass from a '
|
|
'non-frozen one')
|
|
|
|
# Remember all of the fields on our class (including bases). This also
|
|
# marks this class as being a dataclass.
|
|
setattr(cls, _FIELDS, fields)
|
|
|
|
# Was this class defined with an explicit __hash__? Note that if
|
|
# __eq__ is defined in this class, then python will automatically
|
|
# set __hash__ to None. This is a heuristic, as it's possible
|
|
# that such a __hash__ == None was not auto-generated, but it
|
|
# close enough.
|
|
class_hash = cls.__dict__.get('__hash__', MISSING)
|
|
has_explicit_hash = not (class_hash is MISSING or
|
|
(class_hash is None and '__eq__' in cls.__dict__))
|
|
|
|
# If we're generating ordering methods, we must be generating
|
|
# the eq methods.
|
|
if order and not eq:
|
|
raise ValueError('eq must be true if order is true')
|
|
|
|
if init:
|
|
# Does this class have a post-init function?
|
|
has_post_init = hasattr(cls, _POST_INIT_NAME)
|
|
|
|
# Include InitVars and regular fields (so, not ClassVars).
|
|
flds = [f for f in fields.values()
|
|
if f._field_type in (_FIELD, _FIELD_INITVAR)]
|
|
_set_new_attribute(cls, '__init__',
|
|
_init_fn(flds,
|
|
frozen,
|
|
has_post_init,
|
|
# The name to use for the "self" param
|
|
# in __init__. Use "self" if possible.
|
|
'__dataclass_self__' if 'self' in fields
|
|
else 'self',
|
|
))
|
|
|
|
# Get the fields as a list, and include only real fields. This is
|
|
# used in all of the following methods.
|
|
field_list = [f for f in fields.values() if f._field_type is _FIELD]
|
|
|
|
if repr:
|
|
flds = [f for f in field_list if f.repr]
|
|
_set_new_attribute(cls, '__repr__', _repr_fn(flds))
|
|
|
|
if eq:
|
|
# Create _eq__ method. There's no need for a __ne__ method,
|
|
# since python will call __eq__ and negate it.
|
|
flds = [f for f in field_list if f.compare]
|
|
self_tuple = _tuple_str('self', flds)
|
|
other_tuple = _tuple_str('other', flds)
|
|
_set_new_attribute(cls, '__eq__',
|
|
_cmp_fn('__eq__', '==',
|
|
self_tuple, other_tuple))
|
|
|
|
if order:
|
|
# Create and set the ordering methods.
|
|
flds = [f for f in field_list if f.compare]
|
|
self_tuple = _tuple_str('self', flds)
|
|
other_tuple = _tuple_str('other', flds)
|
|
for name, op in [('__lt__', '<'),
|
|
('__le__', '<='),
|
|
('__gt__', '>'),
|
|
('__ge__', '>='),
|
|
]:
|
|
if _set_new_attribute(cls, name,
|
|
_cmp_fn(name, op, self_tuple, other_tuple)):
|
|
raise TypeError(f'Cannot overwrite attribute {name} '
|
|
f'in class {cls.__name__}. Consider using '
|
|
'functools.total_ordering')
|
|
|
|
if frozen:
|
|
for fn in _frozen_get_del_attr(cls, field_list):
|
|
if _set_new_attribute(cls, fn.__name__, fn):
|
|
raise TypeError(f'Cannot overwrite attribute {fn.__name__} '
|
|
f'in class {cls.__name__}')
|
|
|
|
# Decide if/how we're going to create a hash function.
|
|
hash_action = _hash_action[bool(unsafe_hash),
|
|
bool(eq),
|
|
bool(frozen),
|
|
has_explicit_hash]
|
|
if hash_action:
|
|
# No need to call _set_new_attribute here, since by the time
|
|
# we're here the overwriting is unconditional.
|
|
cls.__hash__ = hash_action(cls, field_list)
|
|
|
|
if not getattr(cls, '__doc__'):
|
|
# Create a class doc-string.
|
|
cls.__doc__ = (cls.__name__ +
|
|
str(inspect.signature(cls)).replace(' -> None', ''))
|
|
|
|
return cls
|
|
|
|
|
|
# _cls should never be specified by keyword, so start it with an
|
|
# underscore. The presence of _cls is used to detect if this
|
|
# decorator is being called with parameters or not.
|
|
def dataclass(_cls=None, *, init=True, repr=True, eq=True, order=False,
|
|
unsafe_hash=False, frozen=False):
|
|
"""Returns the same class as was passed in, with dunder methods
|
|
added based on the fields defined in the class.
|
|
|
|
Examines PEP 526 __annotations__ to determine fields.
|
|
|
|
If init is true, an __init__() method is added to the class. If
|
|
repr is true, a __repr__() method is added. If order is true, rich
|
|
comparison dunder methods are added. If unsafe_hash is true, a
|
|
__hash__() method function is added. If frozen is true, fields may
|
|
not be assigned to after instance creation.
|
|
"""
|
|
|
|
def wrap(cls):
|
|
return _process_class(cls, init, repr, eq, order, unsafe_hash, frozen)
|
|
|
|
# See if we're being called as @dataclass or @dataclass().
|
|
if _cls is None:
|
|
# We're called with parens.
|
|
return wrap
|
|
|
|
# We're called as @dataclass without parens.
|
|
return wrap(_cls)
|
|
|
|
|
|
def fields(class_or_instance):
|
|
"""Return a tuple describing the fields of this dataclass.
|
|
|
|
Accepts a dataclass or an instance of one. Tuple elements are of
|
|
type Field.
|
|
"""
|
|
|
|
# Might it be worth caching this, per class?
|
|
try:
|
|
fields = getattr(class_or_instance, _FIELDS)
|
|
except AttributeError:
|
|
raise TypeError('must be called with a dataclass type or instance')
|
|
|
|
# Exclude pseudo-fields. Note that fields is sorted by insertion
|
|
# order, so the order of the tuple is as the fields were defined.
|
|
return tuple(f for f in fields.values() if f._field_type is _FIELD)
|
|
|
|
|
|
def _is_dataclass_instance(obj):
|
|
"""Returns True if obj is an instance of a dataclass."""
|
|
return not isinstance(obj, type) and hasattr(obj, _FIELDS)
|
|
|
|
|
|
def is_dataclass(obj):
|
|
"""Returns True if obj is a dataclass or an instance of a
|
|
dataclass."""
|
|
return hasattr(obj, _FIELDS)
|
|
|
|
|
|
def asdict(obj, *, dict_factory=dict):
|
|
"""Return the fields of a dataclass instance as a new dictionary mapping
|
|
field names to field values.
|
|
|
|
Example usage:
|
|
|
|
@dataclass
|
|
class C:
|
|
x: int
|
|
y: int
|
|
|
|
c = C(1, 2)
|
|
assert asdict(c) == {'x': 1, 'y': 2}
|
|
|
|
If given, 'dict_factory' will be used instead of built-in dict.
|
|
The function applies recursively to field values that are
|
|
dataclass instances. This will also look into built-in containers:
|
|
tuples, lists, and dicts.
|
|
"""
|
|
if not _is_dataclass_instance(obj):
|
|
raise TypeError("asdict() should be called on dataclass instances")
|
|
return _asdict_inner(obj, dict_factory)
|
|
|
|
|
|
def _asdict_inner(obj, dict_factory):
|
|
if _is_dataclass_instance(obj):
|
|
result = []
|
|
for f in fields(obj):
|
|
value = _asdict_inner(getattr(obj, f.name), dict_factory)
|
|
result.append((f.name, value))
|
|
return dict_factory(result)
|
|
elif isinstance(obj, (list, tuple)):
|
|
return type(obj)(_asdict_inner(v, dict_factory) for v in obj)
|
|
elif isinstance(obj, dict):
|
|
return type(obj)((_asdict_inner(k, dict_factory), _asdict_inner(v, dict_factory))
|
|
for k, v in obj.items())
|
|
else:
|
|
return copy.deepcopy(obj)
|
|
|
|
|
|
def astuple(obj, *, tuple_factory=tuple):
|
|
"""Return the fields of a dataclass instance as a new tuple of field values.
|
|
|
|
Example usage::
|
|
|
|
@dataclass
|
|
class C:
|
|
x: int
|
|
y: int
|
|
|
|
c = C(1, 2)
|
|
assert astuple(c) == (1, 2)
|
|
|
|
If given, 'tuple_factory' will be used instead of built-in tuple.
|
|
The function applies recursively to field values that are
|
|
dataclass instances. This will also look into built-in containers:
|
|
tuples, lists, and dicts.
|
|
"""
|
|
|
|
if not _is_dataclass_instance(obj):
|
|
raise TypeError("astuple() should be called on dataclass instances")
|
|
return _astuple_inner(obj, tuple_factory)
|
|
|
|
|
|
def _astuple_inner(obj, tuple_factory):
|
|
if _is_dataclass_instance(obj):
|
|
result = []
|
|
for f in fields(obj):
|
|
value = _astuple_inner(getattr(obj, f.name), tuple_factory)
|
|
result.append(value)
|
|
return tuple_factory(result)
|
|
elif isinstance(obj, (list, tuple)):
|
|
return type(obj)(_astuple_inner(v, tuple_factory) for v in obj)
|
|
elif isinstance(obj, dict):
|
|
return type(obj)((_astuple_inner(k, tuple_factory), _astuple_inner(v, tuple_factory))
|
|
for k, v in obj.items())
|
|
else:
|
|
return copy.deepcopy(obj)
|
|
|
|
|
|
def make_dataclass(cls_name, fields, *, bases=(), namespace=None, init=True,
|
|
repr=True, eq=True, order=False, unsafe_hash=False,
|
|
frozen=False):
|
|
"""Return a new dynamically created dataclass.
|
|
|
|
The dataclass name will be 'cls_name'. 'fields' is an iterable
|
|
of either (name), (name, type) or (name, type, Field) objects. If type is
|
|
omitted, use the string 'typing.Any'. Field objects are created by
|
|
the equivalent of calling 'field(name, type [, Field-info])'.
|
|
|
|
C = make_dataclass('C', ['x', ('y', int), ('z', int, field(init=False))], bases=(Base,))
|
|
|
|
is equivalent to:
|
|
|
|
@dataclass
|
|
class C(Base):
|
|
x: 'typing.Any'
|
|
y: int
|
|
z: int = field(init=False)
|
|
|
|
For the bases and namespace parameters, see the builtin type() function.
|
|
|
|
The parameters init, repr, eq, order, unsafe_hash, and frozen are passed to
|
|
dataclass().
|
|
"""
|
|
|
|
if namespace is None:
|
|
namespace = {}
|
|
else:
|
|
# Copy namespace since we're going to mutate it.
|
|
namespace = namespace.copy()
|
|
|
|
anns = {}
|
|
for item in fields:
|
|
if isinstance(item, str):
|
|
name = item
|
|
tp = 'typing.Any'
|
|
elif len(item) == 2:
|
|
name, tp, = item
|
|
elif len(item) == 3:
|
|
name, tp, spec = item
|
|
namespace[name] = spec
|
|
anns[name] = tp
|
|
|
|
namespace['__annotations__'] = anns
|
|
cls = type(cls_name, bases, namespace)
|
|
return dataclass(cls, init=init, repr=repr, eq=eq, order=order,
|
|
unsafe_hash=unsafe_hash, frozen=frozen)
|
|
|
|
|
|
def replace(obj, **changes):
|
|
"""Return a new object replacing specified fields with new values.
|
|
|
|
This is especially useful for frozen classes. Example usage:
|
|
|
|
@dataclass(frozen=True)
|
|
class C:
|
|
x: int
|
|
y: int
|
|
|
|
c = C(1, 2)
|
|
c1 = replace(c, x=3)
|
|
assert c1.x == 3 and c1.y == 2
|
|
"""
|
|
|
|
# We're going to mutate 'changes', but that's okay because it's a new
|
|
# dict, even if called with 'replace(obj, **my_changes)'.
|
|
|
|
if not _is_dataclass_instance(obj):
|
|
raise TypeError("replace() should be called on dataclass instances")
|
|
|
|
# It's an error to have init=False fields in 'changes'.
|
|
# If a field is not in 'changes', read its value from the provided obj.
|
|
|
|
for f in getattr(obj, _FIELDS).values():
|
|
if not f.init:
|
|
# Error if this field is specified in changes.
|
|
if f.name in changes:
|
|
raise ValueError(f'field {f.name} is declared with '
|
|
'init=False, it cannot be specified with '
|
|
'replace()')
|
|
continue
|
|
|
|
if f.name not in changes:
|
|
changes[f.name] = getattr(obj, f.name)
|
|
|
|
# Create the new object, which calls __init__() and
|
|
# __post_init__() (if defined), using all of the init fields
|
|
# we've added and/or left in 'changes'. If there are values
|
|
# supplied in changes that aren't fields, this will correctly
|
|
# raise a TypeError.
|
|
return obj.__class__(**changes)
|