diff options
Diffstat (limited to 'Lib/dataclasses.py')
| -rw-r--r-- | Lib/dataclasses.py | 184 |
1 files changed, 105 insertions, 79 deletions
diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py index fb279cd..db92b10 100644 --- a/Lib/dataclasses.py +++ b/Lib/dataclasses.py @@ -20,11 +20,11 @@ __all__ = ['dataclass', # Conditions for adding methods. The boxes indicate what action the # dataclass decorator takes. For all of these tables, when I talk -# about init=, repr=, eq=, order=, hash=, or frozen=, I'm referring -# to the arguments to the @dataclass decorator. When checking if a -# dunder method already exists, I mean check for an entry in the -# class's __dict__. I never check to see if an attribute is defined -# in a base class. +# about init=, repr=, eq=, order=, unsafe_hash=, or frozen=, I'm +# referring to the arguments to the @dataclass decorator. When +# checking if a dunder method already exists, I mean check for an +# entry in the class's __dict__. I never check to see if an +# attribute is defined in a base class. # Key: # +=========+=========================================+ @@ -34,11 +34,6 @@ __all__ = ['dataclass', # +---------+-----------------------------------------+ # | add | Generated method is added. | # +---------+-----------------------------------------+ -# | add* | Generated method is added only if the | -# | | existing attribute is None and if the | -# | | user supplied a __eq__ method in the | -# | | class definition. | -# +---------+-----------------------------------------+ # | raise | TypeError is raised. | # +---------+-----------------------------------------+ # | None | Attribute is set to None. | @@ -115,43 +110,36 @@ __all__ = ['dataclass', # __hash__ -# +------------------- hash= parameter -# | +----------- eq= parameter -# | | +--- frozen= parameter -# | | | -# v v v | | | -# | no | yes | <--- class has __hash__ in __dict__? -# +=========+=======+=======+========+========+ -# | 1 None | False | False | | | No __eq__, use the base class __hash__ -# +---------+-------+-------+--------+--------+ -# | 2 None | False | True | | | No __eq__, use the base class __hash__ -# +---------+-------+-------+--------+--------+ -# | 3 None | True | False | None | | <-- the default, not hashable -# +---------+-------+-------+--------+--------+ -# | 4 None | True | True | add | add* | Frozen, so hashable -# +---------+-------+-------+--------+--------+ -# | 5 False | False | False | | | -# +---------+-------+-------+--------+--------+ -# | 6 False | False | True | | | -# +---------+-------+-------+--------+--------+ -# | 7 False | True | False | | | -# +---------+-------+-------+--------+--------+ -# | 8 False | True | True | | | -# +---------+-------+-------+--------+--------+ -# | 9 True | False | False | add | add* | Has no __eq__, but hashable -# +---------+-------+-------+--------+--------+ -# |10 True | False | True | add | add* | Has no __eq__, but hashable -# +---------+-------+-------+--------+--------+ -# |11 True | True | False | add | add* | Not frozen, but hashable -# +---------+-------+-------+--------+--------+ -# |12 True | True | True | add | add* | Frozen, so hashable -# +=========+=======+=======+========+========+ +# +------------------- unsafe_hash= parameter +# | +----------- eq= parameter +# | | +--- frozen= parameter +# | | | +# v v v | | | +# | no | yes | <--- class has explicitly defined __hash__ +# +=======+=======+=======+========+========+ +# | False | False | False | | | No __eq__, use the base class __hash__ +# +-------+-------+-------+--------+--------+ +# | False | False | True | | | No __eq__, use the base class __hash__ +# +-------+-------+-------+--------+--------+ +# | False | True | False | None | | <-- the default, not hashable +# +-------+-------+-------+--------+--------+ +# | False | True | True | add | | Frozen, so hashable, allows override +# +-------+-------+-------+--------+--------+ +# | True | False | False | add | raise | Has no __eq__, but hashable +# +-------+-------+-------+--------+--------+ +# | True | False | True | add | raise | Has no __eq__, but hashable +# +-------+-------+-------+--------+--------+ +# | True | True | False | add | raise | Not frozen, but hashable +# +-------+-------+-------+--------+--------+ +# | True | True | True | add | raise | Frozen, so hashable +# +=======+=======+=======+========+========+ # For boxes that are blank, __hash__ is untouched and therefore # inherited from the base class. If the base is object, then # id-based hashing is used. # Note that a class may have already __hash__=None if it specified an # __eq__ method in the class body (not one that was created by # @dataclass). +# See _hash_action (below) for a coded version of this table. # Raised when an attempt is made to modify a frozen class. @@ -557,7 +545,45 @@ def _set_new_attribute(cls, name, value): return False -def _process_class(cls, repr, eq, order, hash, init, frozen): +# 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. +# Actions: +# '': Do nothing. +# 'none': Set __hash__ to None. +# 'add': Always add a generated __hash__function. +# 'exception': Raise an exception. +# +# +-------------------------------------- unsafe_hash? +# | +------------------------------- eq? +# | | +------------------------ frozen? +# | | | +---------------- has-explicit-hash? +# | | | | +# | | | | +------- action +# | | | | | +# v v v v v +_hash_action = {(False, False, False, False): (''), + (False, False, False, True ): (''), + (False, False, True, False): (''), + (False, False, True, True ): (''), + (False, True, False, False): ('none'), + (False, True, False, True ): (''), + (False, True, True, False): ('add'), + (False, True, True, True ): (''), + (True, False, False, False): ('add'), + (True, False, False, True ): ('exception'), + (True, False, True, False): ('add'), + (True, False, True, True ): ('exception'), + (True, True, False, False): ('add'), + (True, True, False, True ): ('exception'), + (True, True, True, False): ('add'), + (True, True, True, True ): ('exception'), + } +# See https://bugs.python.org/issue32929#msg312829 for an if-statement +# version of this table. + + +def _process_class(cls, repr, eq, order, unsafe_hash, init, 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 @@ -605,8 +631,14 @@ def _process_class(cls, repr, eq, order, hash, init, frozen): # be inherited down. is_frozen = frozen or cls.__setattr__ is _frozen_setattr - # Was this class defined with an __eq__? Used in __hash__ logic. - auto_hash_test= '__eq__' in cls.__dict__ and getattr(cls.__dict__, '__hash__', MISSING) is None + # 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. @@ -661,7 +693,7 @@ def _process_class(cls, repr, eq, order, hash, init, frozen): if _set_new_attribute(cls, name, _cmp_fn(name, op, self_tuple, other_tuple)): raise TypeError(f'Cannot overwrite attribute {name} ' - f'in {cls.__name__}. Consider using ' + f'in class {cls.__name__}. Consider using ' 'functools.total_ordering') if is_frozen: @@ -669,40 +701,30 @@ def _process_class(cls, repr, eq, order, hash, init, frozen): ('__delattr__', _frozen_delattr)]: if _set_new_attribute(cls, name, fn): raise TypeError(f'Cannot overwrite attribute {name} ' - f'in {cls.__name__}') + f'in class {cls.__name__}') # Decide if/how we're going to create a hash function. - # TODO: Move this table to module scope, so it's not recreated - # all the time. - generate_hash = {(None, False, False): ('', ''), - (None, False, True): ('', ''), - (None, True, False): ('none', ''), - (None, True, True): ('fn', 'fn-x'), - (False, False, False): ('', ''), - (False, False, True): ('', ''), - (False, True, False): ('', ''), - (False, True, True): ('', ''), - (True, False, False): ('fn', 'fn-x'), - (True, False, True): ('fn', 'fn-x'), - (True, True, False): ('fn', 'fn-x'), - (True, True, True): ('fn', 'fn-x'), - }[None if hash is None else bool(hash), # Force bool() if not None. - bool(eq), - bool(frozen)]['__hash__' in cls.__dict__] + hash_action = _hash_action[bool(unsafe_hash), + bool(eq), + bool(frozen), + has_explicit_hash] + # No need to call _set_new_attribute here, since we already know if # we're overwriting a __hash__ or not. - if generate_hash == '': + if hash_action == '': # Do nothing. pass - elif generate_hash == 'none': + elif hash_action == 'none': cls.__hash__ = None - elif generate_hash in ('fn', 'fn-x'): - if generate_hash == 'fn' or auto_hash_test: - flds = [f for f in field_list - if (f.compare if f.hash is None else f.hash)] - cls.__hash__ = _hash_fn(flds) + elif hash_action == 'add': + flds = [f for f in field_list if (f.compare if f.hash is None else f.hash)] + cls.__hash__ = _hash_fn(flds) + elif hash_action == 'exception': + # Raise an exception. + raise TypeError(f'Cannot overwrite attribute __hash__ ' + f'in class {cls.__name__}') else: - assert False, f"can't get here: {generate_hash}" + assert False, f"can't get here: {hash_action}" if not getattr(cls, '__doc__'): # Create a class doc-string. @@ -716,7 +738,7 @@ def _process_class(cls, repr, eq, order, hash, init, frozen): # 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, - hash=None, frozen=False): + unsafe_hash=None, frozen=False): """Returns the same class as was passed in, with dunder methods added based on the fields defined in the class. @@ -724,13 +746,13 @@ def dataclass(_cls=None, *, init=True, repr=True, eq=True, order=False, 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 hash is true, a __hash__() - method function is added. If frozen is true, fields may not be - assigned to after instance creation. + 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, repr, eq, order, hash, init, frozen) + return _process_class(cls, repr, eq, order, unsafe_hash, init, frozen) # See if we're being called as @dataclass or @dataclass(). if _cls is None: @@ -793,6 +815,7 @@ def asdict(obj, *, dict_factory=dict): 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 = [] @@ -832,6 +855,7 @@ def astuple(obj, *, tuple_factory=tuple): 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 = [] @@ -849,7 +873,8 @@ def _astuple_inner(obj, tuple_factory): def make_dataclass(cls_name, fields, *, bases=(), namespace=None, init=True, - repr=True, eq=True, order=False, hash=None, frozen=False): + repr=True, eq=True, order=False, unsafe_hash=None, + frozen=False): """Return a new dynamically created dataclass. The dataclass name will be 'cls_name'. 'fields' is an iterable @@ -869,7 +894,7 @@ def make_dataclass(cls_name, fields, *, bases=(), namespace=None, init=True, For the bases and namespace parameters, see the builtin type() function. - The parameters init, repr, eq, order, hash, and frozen are passed to + The parameters init, repr, eq, order, unsafe_hash, and frozen are passed to dataclass(). """ @@ -894,7 +919,8 @@ def make_dataclass(cls_name, fields, *, bases=(), namespace=None, init=True, namespace['__annotations__'] = anns cls = type(cls_name, bases, namespace) return dataclass(cls, init=init, repr=repr, eq=eq, order=order, - hash=hash, frozen=frozen) + unsafe_hash=unsafe_hash, frozen=frozen) + def replace(obj, **changes): """Return a new object replacing specified fields with new values. |