Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 1 | import sys |
| 2 | import types |
| 3 | from copy import deepcopy |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 4 | import inspect |
| 5 | |
| 6 | __all__ = ['dataclass', |
| 7 | 'field', |
| 8 | 'FrozenInstanceError', |
| 9 | 'InitVar', |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 10 | 'MISSING', |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 11 | |
| 12 | # Helper functions. |
| 13 | 'fields', |
| 14 | 'asdict', |
| 15 | 'astuple', |
| 16 | 'make_dataclass', |
| 17 | 'replace', |
Eric V. Smith | e7ba013 | 2018-01-06 12:41:53 -0500 | [diff] [blame] | 18 | 'is_dataclass', |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 19 | ] |
| 20 | |
Eric V. Smith | ea8fc52 | 2018-01-27 19:07:40 -0500 | [diff] [blame] | 21 | # Conditions for adding methods. The boxes indicate what action the |
| 22 | # dataclass decorator takes. For all of these tables, when I talk |
| 23 | # about init=, repr=, eq=, order=, hash=, or frozen=, I'm referring |
| 24 | # to the arguments to the @dataclass decorator. When checking if a |
| 25 | # dunder method already exists, I mean check for an entry in the |
| 26 | # class's __dict__. I never check to see if an attribute is defined |
| 27 | # in a base class. |
| 28 | |
| 29 | # Key: |
| 30 | # +=========+=========================================+ |
| 31 | # + Value | Meaning | |
| 32 | # +=========+=========================================+ |
| 33 | # | <blank> | No action: no method is added. | |
| 34 | # +---------+-----------------------------------------+ |
| 35 | # | add | Generated method is added. | |
| 36 | # +---------+-----------------------------------------+ |
| 37 | # | add* | Generated method is added only if the | |
| 38 | # | | existing attribute is None and if the | |
| 39 | # | | user supplied a __eq__ method in the | |
| 40 | # | | class definition. | |
| 41 | # +---------+-----------------------------------------+ |
| 42 | # | raise | TypeError is raised. | |
| 43 | # +---------+-----------------------------------------+ |
| 44 | # | None | Attribute is set to None. | |
| 45 | # +=========+=========================================+ |
| 46 | |
| 47 | # __init__ |
| 48 | # |
| 49 | # +--- init= parameter |
| 50 | # | |
| 51 | # v | | | |
| 52 | # | no | yes | <--- class has __init__ in __dict__? |
| 53 | # +=======+=======+=======+ |
| 54 | # | False | | | |
| 55 | # +-------+-------+-------+ |
| 56 | # | True | add | | <- the default |
| 57 | # +=======+=======+=======+ |
| 58 | |
| 59 | # __repr__ |
| 60 | # |
| 61 | # +--- repr= parameter |
| 62 | # | |
| 63 | # v | | | |
| 64 | # | no | yes | <--- class has __repr__ in __dict__? |
| 65 | # +=======+=======+=======+ |
| 66 | # | False | | | |
| 67 | # +-------+-------+-------+ |
| 68 | # | True | add | | <- the default |
| 69 | # +=======+=======+=======+ |
| 70 | |
| 71 | |
| 72 | # __setattr__ |
| 73 | # __delattr__ |
| 74 | # |
| 75 | # +--- frozen= parameter |
| 76 | # | |
| 77 | # v | | | |
| 78 | # | no | yes | <--- class has __setattr__ or __delattr__ in __dict__? |
| 79 | # +=======+=======+=======+ |
| 80 | # | False | | | <- the default |
| 81 | # +-------+-------+-------+ |
| 82 | # | True | add | raise | |
| 83 | # +=======+=======+=======+ |
| 84 | # Raise because not adding these methods would break the "frozen-ness" |
| 85 | # of the class. |
| 86 | |
| 87 | # __eq__ |
| 88 | # |
| 89 | # +--- eq= parameter |
| 90 | # | |
| 91 | # v | | | |
| 92 | # | no | yes | <--- class has __eq__ in __dict__? |
| 93 | # +=======+=======+=======+ |
| 94 | # | False | | | |
| 95 | # +-------+-------+-------+ |
| 96 | # | True | add | | <- the default |
| 97 | # +=======+=======+=======+ |
| 98 | |
| 99 | # __lt__ |
| 100 | # __le__ |
| 101 | # __gt__ |
| 102 | # __ge__ |
| 103 | # |
| 104 | # +--- order= parameter |
| 105 | # | |
| 106 | # v | | | |
| 107 | # | no | yes | <--- class has any comparison method in __dict__? |
| 108 | # +=======+=======+=======+ |
| 109 | # | False | | | <- the default |
| 110 | # +-------+-------+-------+ |
| 111 | # | True | add | raise | |
| 112 | # +=======+=======+=======+ |
| 113 | # Raise because to allow this case would interfere with using |
| 114 | # functools.total_ordering. |
| 115 | |
| 116 | # __hash__ |
| 117 | |
| 118 | # +------------------- hash= parameter |
| 119 | # | +----------- eq= parameter |
| 120 | # | | +--- frozen= parameter |
| 121 | # | | | |
| 122 | # v v v | | | |
| 123 | # | no | yes | <--- class has __hash__ in __dict__? |
| 124 | # +=========+=======+=======+========+========+ |
| 125 | # | 1 None | False | False | | | No __eq__, use the base class __hash__ |
| 126 | # +---------+-------+-------+--------+--------+ |
| 127 | # | 2 None | False | True | | | No __eq__, use the base class __hash__ |
| 128 | # +---------+-------+-------+--------+--------+ |
| 129 | # | 3 None | True | False | None | | <-- the default, not hashable |
| 130 | # +---------+-------+-------+--------+--------+ |
| 131 | # | 4 None | True | True | add | add* | Frozen, so hashable |
| 132 | # +---------+-------+-------+--------+--------+ |
| 133 | # | 5 False | False | False | | | |
| 134 | # +---------+-------+-------+--------+--------+ |
| 135 | # | 6 False | False | True | | | |
| 136 | # +---------+-------+-------+--------+--------+ |
| 137 | # | 7 False | True | False | | | |
| 138 | # +---------+-------+-------+--------+--------+ |
| 139 | # | 8 False | True | True | | | |
| 140 | # +---------+-------+-------+--------+--------+ |
| 141 | # | 9 True | False | False | add | add* | Has no __eq__, but hashable |
| 142 | # +---------+-------+-------+--------+--------+ |
| 143 | # |10 True | False | True | add | add* | Has no __eq__, but hashable |
| 144 | # +---------+-------+-------+--------+--------+ |
| 145 | # |11 True | True | False | add | add* | Not frozen, but hashable |
| 146 | # +---------+-------+-------+--------+--------+ |
| 147 | # |12 True | True | True | add | add* | Frozen, so hashable |
| 148 | # +=========+=======+=======+========+========+ |
| 149 | # For boxes that are blank, __hash__ is untouched and therefore |
| 150 | # inherited from the base class. If the base is object, then |
| 151 | # id-based hashing is used. |
| 152 | # Note that a class may have already __hash__=None if it specified an |
| 153 | # __eq__ method in the class body (not one that was created by |
| 154 | # @dataclass). |
| 155 | |
| 156 | |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 157 | # Raised when an attempt is made to modify a frozen class. |
| 158 | class FrozenInstanceError(AttributeError): pass |
| 159 | |
| 160 | # A sentinel object for default values to signal that a |
| 161 | # default-factory will be used. |
| 162 | # This is given a nice repr() which will appear in the function |
| 163 | # signature of dataclasses' constructors. |
| 164 | class _HAS_DEFAULT_FACTORY_CLASS: |
| 165 | def __repr__(self): |
| 166 | return '<factory>' |
| 167 | _HAS_DEFAULT_FACTORY = _HAS_DEFAULT_FACTORY_CLASS() |
| 168 | |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 169 | # A sentinel object to detect if a parameter is supplied or not. Use |
| 170 | # a class to give it a better repr. |
| 171 | class _MISSING_TYPE: |
| 172 | pass |
| 173 | MISSING = _MISSING_TYPE() |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 174 | |
| 175 | # Since most per-field metadata will be unused, create an empty |
| 176 | # read-only proxy that can be shared among all fields. |
| 177 | _EMPTY_METADATA = types.MappingProxyType({}) |
| 178 | |
| 179 | # Markers for the various kinds of fields and pseudo-fields. |
| 180 | _FIELD = object() # An actual field. |
| 181 | _FIELD_CLASSVAR = object() # Not a field, but a ClassVar. |
| 182 | _FIELD_INITVAR = object() # Not a field, but an InitVar. |
| 183 | |
| 184 | # The name of an attribute on the class where we store the Field |
| 185 | # objects. Also used to check if a class is a Data Class. |
| 186 | _MARKER = '__dataclass_fields__' |
| 187 | |
| 188 | # The name of the function, that if it exists, is called at the end of |
| 189 | # __init__. |
| 190 | _POST_INIT_NAME = '__post_init__' |
| 191 | |
| 192 | |
| 193 | class _InitVarMeta(type): |
| 194 | def __getitem__(self, params): |
| 195 | return self |
| 196 | |
| 197 | class InitVar(metaclass=_InitVarMeta): |
| 198 | pass |
| 199 | |
| 200 | |
| 201 | # Instances of Field are only ever created from within this module, |
| 202 | # and only from the field() function, although Field instances are |
| 203 | # exposed externally as (conceptually) read-only objects. |
| 204 | # name and type are filled in after the fact, not in __init__. They're |
| 205 | # not known at the time this class is instantiated, but it's |
| 206 | # convenient if they're available later. |
| 207 | # When cls._MARKER is filled in with a list of Field objects, the name |
| 208 | # and type fields will have been populated. |
| 209 | class Field: |
| 210 | __slots__ = ('name', |
| 211 | 'type', |
| 212 | 'default', |
| 213 | 'default_factory', |
| 214 | 'repr', |
| 215 | 'hash', |
| 216 | 'init', |
| 217 | 'compare', |
| 218 | 'metadata', |
| 219 | '_field_type', # Private: not to be used by user code. |
| 220 | ) |
| 221 | |
| 222 | def __init__(self, default, default_factory, init, repr, hash, compare, |
| 223 | metadata): |
| 224 | self.name = None |
| 225 | self.type = None |
| 226 | self.default = default |
| 227 | self.default_factory = default_factory |
| 228 | self.init = init |
| 229 | self.repr = repr |
| 230 | self.hash = hash |
| 231 | self.compare = compare |
| 232 | self.metadata = (_EMPTY_METADATA |
| 233 | if metadata is None or len(metadata) == 0 else |
| 234 | types.MappingProxyType(metadata)) |
| 235 | self._field_type = None |
| 236 | |
| 237 | def __repr__(self): |
| 238 | return ('Field(' |
| 239 | f'name={self.name!r},' |
| 240 | f'type={self.type},' |
| 241 | f'default={self.default},' |
| 242 | f'default_factory={self.default_factory},' |
| 243 | f'init={self.init},' |
| 244 | f'repr={self.repr},' |
| 245 | f'hash={self.hash},' |
| 246 | f'compare={self.compare},' |
| 247 | f'metadata={self.metadata}' |
| 248 | ')') |
| 249 | |
| 250 | |
| 251 | # This function is used instead of exposing Field creation directly, |
| 252 | # so that a type checker can be told (via overloads) that this is a |
| 253 | # function whose type depends on its parameters. |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 254 | def field(*, default=MISSING, default_factory=MISSING, init=True, repr=True, |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 255 | hash=None, compare=True, metadata=None): |
| 256 | """Return an object to identify dataclass fields. |
| 257 | |
| 258 | default is the default value of the field. default_factory is a |
| 259 | 0-argument function called to initialize a field's value. If init |
| 260 | is True, the field will be a parameter to the class's __init__() |
| 261 | function. If repr is True, the field will be included in the |
| 262 | object's repr(). If hash is True, the field will be included in |
| 263 | the object's hash(). If compare is True, the field will be used in |
| 264 | comparison functions. metadata, if specified, must be a mapping |
| 265 | which is stored but not otherwise examined by dataclass. |
| 266 | |
| 267 | It is an error to specify both default and default_factory. |
| 268 | """ |
| 269 | |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 270 | if default is not MISSING and default_factory is not MISSING: |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 271 | raise ValueError('cannot specify both default and default_factory') |
| 272 | return Field(default, default_factory, init, repr, hash, compare, |
| 273 | metadata) |
| 274 | |
| 275 | |
| 276 | def _tuple_str(obj_name, fields): |
| 277 | # Return a string representing each field of obj_name as a tuple |
| 278 | # member. So, if fields is ['x', 'y'] and obj_name is "self", |
| 279 | # return "(self.x,self.y)". |
| 280 | |
| 281 | # Special case for the 0-tuple. |
Eric V. Smith | ea8fc52 | 2018-01-27 19:07:40 -0500 | [diff] [blame] | 282 | if not fields: |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 283 | return '()' |
| 284 | # Note the trailing comma, needed if this turns out to be a 1-tuple. |
| 285 | return f'({",".join([f"{obj_name}.{f.name}" for f in fields])},)' |
| 286 | |
| 287 | |
Eric V. Smith | ea8fc52 | 2018-01-27 19:07:40 -0500 | [diff] [blame] | 288 | def _create_fn(name, args, body, *, globals=None, locals=None, |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 289 | return_type=MISSING): |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 290 | # Note that we mutate locals when exec() is called. Caller beware! |
| 291 | if locals is None: |
| 292 | locals = {} |
| 293 | return_annotation = '' |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 294 | if return_type is not MISSING: |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 295 | locals['_return_type'] = return_type |
| 296 | return_annotation = '->_return_type' |
| 297 | args = ','.join(args) |
| 298 | body = '\n'.join(f' {b}' for b in body) |
| 299 | |
| 300 | txt = f'def {name}({args}){return_annotation}:\n{body}' |
| 301 | |
| 302 | exec(txt, globals, locals) |
| 303 | return locals[name] |
| 304 | |
| 305 | |
| 306 | def _field_assign(frozen, name, value, self_name): |
| 307 | # If we're a frozen class, then assign to our fields in __init__ |
| 308 | # via object.__setattr__. Otherwise, just use a simple |
| 309 | # assignment. |
| 310 | # self_name is what "self" is called in this function: don't |
| 311 | # hard-code "self", since that might be a field name. |
| 312 | if frozen: |
| 313 | return f'object.__setattr__({self_name},{name!r},{value})' |
| 314 | return f'{self_name}.{name}={value}' |
| 315 | |
| 316 | |
| 317 | def _field_init(f, frozen, globals, self_name): |
| 318 | # Return the text of the line in the body of __init__ that will |
| 319 | # initialize this field. |
| 320 | |
| 321 | default_name = f'_dflt_{f.name}' |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 322 | if f.default_factory is not MISSING: |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 323 | if f.init: |
| 324 | # This field has a default factory. If a parameter is |
| 325 | # given, use it. If not, call the factory. |
| 326 | globals[default_name] = f.default_factory |
| 327 | value = (f'{default_name}() ' |
| 328 | f'if {f.name} is _HAS_DEFAULT_FACTORY ' |
| 329 | f'else {f.name}') |
| 330 | else: |
| 331 | # This is a field that's not in the __init__ params, but |
| 332 | # has a default factory function. It needs to be |
| 333 | # initialized here by calling the factory function, |
| 334 | # because there's no other way to initialize it. |
| 335 | |
| 336 | # For a field initialized with a default=defaultvalue, the |
| 337 | # class dict just has the default value |
| 338 | # (cls.fieldname=defaultvalue). But that won't work for a |
| 339 | # default factory, the factory must be called in __init__ |
| 340 | # and we must assign that to self.fieldname. We can't |
| 341 | # fall back to the class dict's value, both because it's |
| 342 | # not set, and because it might be different per-class |
| 343 | # (which, after all, is why we have a factory function!). |
| 344 | |
| 345 | globals[default_name] = f.default_factory |
| 346 | value = f'{default_name}()' |
| 347 | else: |
| 348 | # No default factory. |
| 349 | if f.init: |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 350 | if f.default is MISSING: |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 351 | # There's no default, just do an assignment. |
| 352 | value = f.name |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 353 | elif f.default is not MISSING: |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 354 | globals[default_name] = f.default |
| 355 | value = f.name |
| 356 | else: |
| 357 | # This field does not need initialization. Signify that to |
| 358 | # the caller by returning None. |
| 359 | return None |
| 360 | |
| 361 | # Only test this now, so that we can create variables for the |
| 362 | # default. However, return None to signify that we're not going |
| 363 | # to actually do the assignment statement for InitVars. |
| 364 | if f._field_type == _FIELD_INITVAR: |
| 365 | return None |
| 366 | |
| 367 | # Now, actually generate the field assignment. |
| 368 | return _field_assign(frozen, f.name, value, self_name) |
| 369 | |
| 370 | |
| 371 | def _init_param(f): |
| 372 | # Return the __init__ parameter string for this field. |
| 373 | # For example, the equivalent of 'x:int=3' (except instead of 'int', |
| 374 | # reference a variable set to int, and instead of '3', reference a |
| 375 | # variable set to 3). |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 376 | if f.default is MISSING and f.default_factory is MISSING: |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 377 | # There's no default, and no default_factory, just |
| 378 | # output the variable name and type. |
| 379 | default = '' |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 380 | elif f.default is not MISSING: |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 381 | # There's a default, this will be the name that's used to look it up. |
| 382 | default = f'=_dflt_{f.name}' |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 383 | elif f.default_factory is not MISSING: |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 384 | # There's a factory function. Set a marker. |
| 385 | default = '=_HAS_DEFAULT_FACTORY' |
| 386 | return f'{f.name}:_type_{f.name}{default}' |
| 387 | |
| 388 | |
| 389 | def _init_fn(fields, frozen, has_post_init, self_name): |
| 390 | # fields contains both real fields and InitVar pseudo-fields. |
| 391 | |
| 392 | # Make sure we don't have fields without defaults following fields |
| 393 | # with defaults. This actually would be caught when exec-ing the |
| 394 | # function source code, but catching it here gives a better error |
| 395 | # message, and future-proofs us in case we build up the function |
| 396 | # using ast. |
| 397 | seen_default = False |
| 398 | for f in fields: |
| 399 | # Only consider fields in the __init__ call. |
| 400 | if f.init: |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 401 | if not (f.default is MISSING and f.default_factory is MISSING): |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 402 | seen_default = True |
| 403 | elif seen_default: |
| 404 | raise TypeError(f'non-default argument {f.name!r} ' |
| 405 | 'follows default argument') |
| 406 | |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 407 | globals = {'MISSING': MISSING, |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 408 | '_HAS_DEFAULT_FACTORY': _HAS_DEFAULT_FACTORY} |
| 409 | |
| 410 | body_lines = [] |
| 411 | for f in fields: |
| 412 | # Do not initialize the pseudo-fields, only the real ones. |
| 413 | line = _field_init(f, frozen, globals, self_name) |
| 414 | if line is not None: |
| 415 | # line is None means that this field doesn't require |
| 416 | # initialization. Just skip it. |
| 417 | body_lines.append(line) |
| 418 | |
| 419 | # Does this class have a post-init function? |
| 420 | if has_post_init: |
| 421 | params_str = ','.join(f.name for f in fields |
| 422 | if f._field_type is _FIELD_INITVAR) |
| 423 | body_lines += [f'{self_name}.{_POST_INIT_NAME}({params_str})'] |
| 424 | |
| 425 | # If no body lines, use 'pass'. |
Eric V. Smith | ea8fc52 | 2018-01-27 19:07:40 -0500 | [diff] [blame] | 426 | if not body_lines: |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 427 | body_lines = ['pass'] |
| 428 | |
| 429 | locals = {f'_type_{f.name}': f.type for f in fields} |
| 430 | return _create_fn('__init__', |
| 431 | [self_name] +[_init_param(f) for f in fields if f.init], |
| 432 | body_lines, |
| 433 | locals=locals, |
| 434 | globals=globals, |
| 435 | return_type=None) |
| 436 | |
| 437 | |
| 438 | def _repr_fn(fields): |
| 439 | return _create_fn('__repr__', |
| 440 | ['self'], |
| 441 | ['return self.__class__.__qualname__ + f"(' + |
| 442 | ', '.join([f"{f.name}={{self.{f.name}!r}}" |
| 443 | for f in fields]) + |
| 444 | ')"']) |
| 445 | |
| 446 | |
| 447 | def _frozen_setattr(self, name, value): |
| 448 | raise FrozenInstanceError(f'cannot assign to field {name!r}') |
| 449 | |
| 450 | |
| 451 | def _frozen_delattr(self, name): |
| 452 | raise FrozenInstanceError(f'cannot delete field {name!r}') |
| 453 | |
| 454 | |
| 455 | def _cmp_fn(name, op, self_tuple, other_tuple): |
| 456 | # Create a comparison function. If the fields in the object are |
| 457 | # named 'x' and 'y', then self_tuple is the string |
| 458 | # '(self.x,self.y)' and other_tuple is the string |
| 459 | # '(other.x,other.y)'. |
| 460 | |
| 461 | return _create_fn(name, |
| 462 | ['self', 'other'], |
| 463 | [ 'if other.__class__ is self.__class__:', |
| 464 | f' return {self_tuple}{op}{other_tuple}', |
| 465 | 'return NotImplemented']) |
| 466 | |
| 467 | |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 468 | def _hash_fn(fields): |
| 469 | self_tuple = _tuple_str('self', fields) |
| 470 | return _create_fn('__hash__', |
| 471 | ['self'], |
| 472 | [f'return hash({self_tuple})']) |
| 473 | |
| 474 | |
| 475 | def _get_field(cls, a_name, a_type): |
| 476 | # Return a Field object, for this field name and type. ClassVars |
| 477 | # and InitVars are also returned, but marked as such (see |
| 478 | # f._field_type). |
| 479 | |
| 480 | # If the default value isn't derived from field, then it's |
| 481 | # only a normal default value. Convert it to a Field(). |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 482 | default = getattr(cls, a_name, MISSING) |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 483 | if isinstance(default, Field): |
| 484 | f = default |
| 485 | else: |
| 486 | f = field(default=default) |
| 487 | |
| 488 | # Assume it's a normal field until proven otherwise. |
| 489 | f._field_type = _FIELD |
| 490 | |
| 491 | # Only at this point do we know the name and the type. Set them. |
| 492 | f.name = a_name |
| 493 | f.type = a_type |
| 494 | |
| 495 | # If typing has not been imported, then it's impossible for |
| 496 | # any annotation to be a ClassVar. So, only look for ClassVar |
| 497 | # if typing has been imported. |
| 498 | typing = sys.modules.get('typing') |
| 499 | if typing is not None: |
| 500 | # This test uses a typing internal class, but it's the best |
| 501 | # way to test if this is a ClassVar. |
Ivan Levkivskyi | d911e40 | 2018-01-20 11:23:59 +0000 | [diff] [blame] | 502 | if (type(a_type) is typing._GenericAlias and |
| 503 | a_type.__origin__ is typing.ClassVar): |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 504 | # This field is a ClassVar, so it's not a field. |
| 505 | f._field_type = _FIELD_CLASSVAR |
| 506 | |
| 507 | if f._field_type is _FIELD: |
| 508 | # Check if this is an InitVar. |
| 509 | if a_type is InitVar: |
| 510 | # InitVars are not fields, either. |
| 511 | f._field_type = _FIELD_INITVAR |
| 512 | |
| 513 | # Validations for fields. This is delayed until now, instead of |
| 514 | # in the Field() constructor, since only here do we know the field |
| 515 | # name, which allows better error reporting. |
| 516 | |
| 517 | # Special restrictions for ClassVar and InitVar. |
| 518 | if f._field_type in (_FIELD_CLASSVAR, _FIELD_INITVAR): |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 519 | if f.default_factory is not MISSING: |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 520 | raise TypeError(f'field {f.name} cannot have a ' |
| 521 | 'default factory') |
| 522 | # Should I check for other field settings? default_factory |
| 523 | # seems the most serious to check for. Maybe add others. For |
| 524 | # example, how about init=False (or really, |
| 525 | # init=<not-the-default-init-value>)? It makes no sense for |
| 526 | # ClassVar and InitVar to specify init=<anything>. |
| 527 | |
| 528 | # For real fields, disallow mutable defaults for known types. |
| 529 | if f._field_type is _FIELD and isinstance(f.default, (list, dict, set)): |
| 530 | raise ValueError(f'mutable default {type(f.default)} for field ' |
| 531 | f'{f.name} is not allowed: use default_factory') |
| 532 | |
| 533 | return f |
| 534 | |
| 535 | |
| 536 | def _find_fields(cls): |
| 537 | # Return a list of Field objects, in order, for this class (and no |
| 538 | # base classes). Fields are found from __annotations__ (which is |
| 539 | # guaranteed to be ordered). Default values are from class |
| 540 | # attributes, if a field has a default. If the default value is |
| 541 | # a Field(), then it contains additional info beyond (and |
| 542 | # possibly including) the actual default value. Pseudo-fields |
| 543 | # ClassVars and InitVars are included, despite the fact that |
Eric V. Smith | ea8fc52 | 2018-01-27 19:07:40 -0500 | [diff] [blame] | 544 | # they're not real fields. That's dealt with later. |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 545 | |
| 546 | annotations = getattr(cls, '__annotations__', {}) |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 547 | return [_get_field(cls, a_name, a_type) |
| 548 | for a_name, a_type in annotations.items()] |
| 549 | |
| 550 | |
Eric V. Smith | ea8fc52 | 2018-01-27 19:07:40 -0500 | [diff] [blame] | 551 | def _set_new_attribute(cls, name, value): |
| 552 | # Never overwrites an existing attribute. Returns True if the |
| 553 | # attribute already exists. |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 554 | if name in cls.__dict__: |
Eric V. Smith | ea8fc52 | 2018-01-27 19:07:40 -0500 | [diff] [blame] | 555 | return True |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 556 | setattr(cls, name, value) |
Eric V. Smith | ea8fc52 | 2018-01-27 19:07:40 -0500 | [diff] [blame] | 557 | return False |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 558 | |
| 559 | |
| 560 | def _process_class(cls, repr, eq, order, hash, init, frozen): |
Eric V. Smith | d138892 | 2018-01-07 14:30:17 -0500 | [diff] [blame] | 561 | # Now that dicts retain insertion order, there's no reason to use |
| 562 | # an ordered dict. I am leveraging that ordering here, because |
| 563 | # derived class fields overwrite base class fields, but the order |
| 564 | # is defined by the base class, which is found first. |
| 565 | fields = {} |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 566 | |
| 567 | # Find our base classes in reverse MRO order, and exclude |
| 568 | # ourselves. In reversed order so that more derived classes |
| 569 | # override earlier field definitions in base classes. |
| 570 | for b in cls.__mro__[-1:0:-1]: |
| 571 | # Only process classes that have been processed by our |
| 572 | # decorator. That is, they have a _MARKER attribute. |
| 573 | base_fields = getattr(b, _MARKER, None) |
| 574 | if base_fields: |
| 575 | for f in base_fields.values(): |
| 576 | fields[f.name] = f |
| 577 | |
| 578 | # Now find fields in our class. While doing so, validate some |
| 579 | # things, and set the default values (as class attributes) |
| 580 | # where we can. |
| 581 | for f in _find_fields(cls): |
| 582 | fields[f.name] = f |
| 583 | |
| 584 | # If the class attribute (which is the default value for |
| 585 | # this field) exists and is of type 'Field', replace it |
| 586 | # with the real default. This is so that normal class |
| 587 | # introspection sees a real default value, not a Field. |
| 588 | if isinstance(getattr(cls, f.name, None), Field): |
Eric V. Smith | 03220fd | 2017-12-29 13:59:58 -0500 | [diff] [blame] | 589 | if f.default is MISSING: |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 590 | # If there's no default, delete the class attribute. |
| 591 | # This happens if we specify field(repr=False), for |
| 592 | # example (that is, we specified a field object, but |
| 593 | # no default value). Also if we're using a default |
| 594 | # factory. The class attribute should not be set at |
| 595 | # all in the post-processed class. |
| 596 | delattr(cls, f.name) |
| 597 | else: |
| 598 | setattr(cls, f.name, f.default) |
| 599 | |
| 600 | # Remember all of the fields on our class (including bases). This |
| 601 | # marks this class as being a dataclass. |
| 602 | setattr(cls, _MARKER, fields) |
| 603 | |
| 604 | # We also need to check if a parent class is frozen: frozen has to |
| 605 | # be inherited down. |
| 606 | is_frozen = frozen or cls.__setattr__ is _frozen_setattr |
| 607 | |
Eric V. Smith | ea8fc52 | 2018-01-27 19:07:40 -0500 | [diff] [blame] | 608 | # Was this class defined with an __eq__? Used in __hash__ logic. |
| 609 | auto_hash_test= '__eq__' in cls.__dict__ and getattr(cls.__dict__, '__hash__', MISSING) is None |
| 610 | |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 611 | # If we're generating ordering methods, we must be generating |
| 612 | # the eq methods. |
| 613 | if order and not eq: |
| 614 | raise ValueError('eq must be true if order is true') |
| 615 | |
| 616 | if init: |
| 617 | # Does this class have a post-init function? |
| 618 | has_post_init = hasattr(cls, _POST_INIT_NAME) |
| 619 | |
| 620 | # Include InitVars and regular fields (so, not ClassVars). |
Eric V. Smith | ea8fc52 | 2018-01-27 19:07:40 -0500 | [diff] [blame] | 621 | flds = [f for f in fields.values() |
| 622 | if f._field_type in (_FIELD, _FIELD_INITVAR)] |
| 623 | _set_new_attribute(cls, '__init__', |
| 624 | _init_fn(flds, |
| 625 | is_frozen, |
| 626 | has_post_init, |
| 627 | # The name to use for the "self" param |
| 628 | # in __init__. Use "self" if possible. |
| 629 | '__dataclass_self__' if 'self' in fields |
| 630 | else 'self', |
| 631 | )) |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 632 | |
| 633 | # Get the fields as a list, and include only real fields. This is |
| 634 | # used in all of the following methods. |
Eric V. Smith | ea8fc52 | 2018-01-27 19:07:40 -0500 | [diff] [blame] | 635 | field_list = [f for f in fields.values() if f._field_type is _FIELD] |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 636 | |
| 637 | if repr: |
Eric V. Smith | ea8fc52 | 2018-01-27 19:07:40 -0500 | [diff] [blame] | 638 | flds = [f for f in field_list if f.repr] |
| 639 | _set_new_attribute(cls, '__repr__', _repr_fn(flds)) |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 640 | |
| 641 | if eq: |
Eric V. Smith | ea8fc52 | 2018-01-27 19:07:40 -0500 | [diff] [blame] | 642 | # Create _eq__ method. There's no need for a __ne__ method, |
| 643 | # since python will call __eq__ and negate it. |
| 644 | flds = [f for f in field_list if f.compare] |
| 645 | self_tuple = _tuple_str('self', flds) |
| 646 | other_tuple = _tuple_str('other', flds) |
| 647 | _set_new_attribute(cls, '__eq__', |
| 648 | _cmp_fn('__eq__', '==', |
| 649 | self_tuple, other_tuple)) |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 650 | |
| 651 | if order: |
Eric V. Smith | ea8fc52 | 2018-01-27 19:07:40 -0500 | [diff] [blame] | 652 | # Create and set the ordering methods. |
| 653 | flds = [f for f in field_list if f.compare] |
| 654 | self_tuple = _tuple_str('self', flds) |
| 655 | other_tuple = _tuple_str('other', flds) |
| 656 | for name, op in [('__lt__', '<'), |
| 657 | ('__le__', '<='), |
| 658 | ('__gt__', '>'), |
| 659 | ('__ge__', '>='), |
| 660 | ]: |
| 661 | if _set_new_attribute(cls, name, |
| 662 | _cmp_fn(name, op, self_tuple, other_tuple)): |
| 663 | raise TypeError(f'Cannot overwrite attribute {name} ' |
| 664 | f'in {cls.__name__}. Consider using ' |
| 665 | 'functools.total_ordering') |
| 666 | |
| 667 | if is_frozen: |
| 668 | for name, fn in [('__setattr__', _frozen_setattr), |
| 669 | ('__delattr__', _frozen_delattr)]: |
| 670 | if _set_new_attribute(cls, name, fn): |
| 671 | raise TypeError(f'Cannot overwrite attribute {name} ' |
| 672 | f'in {cls.__name__}') |
| 673 | |
| 674 | # Decide if/how we're going to create a hash function. |
| 675 | # TODO: Move this table to module scope, so it's not recreated |
| 676 | # all the time. |
| 677 | generate_hash = {(None, False, False): ('', ''), |
| 678 | (None, False, True): ('', ''), |
| 679 | (None, True, False): ('none', ''), |
| 680 | (None, True, True): ('fn', 'fn-x'), |
| 681 | (False, False, False): ('', ''), |
| 682 | (False, False, True): ('', ''), |
| 683 | (False, True, False): ('', ''), |
| 684 | (False, True, True): ('', ''), |
| 685 | (True, False, False): ('fn', 'fn-x'), |
| 686 | (True, False, True): ('fn', 'fn-x'), |
| 687 | (True, True, False): ('fn', 'fn-x'), |
| 688 | (True, True, True): ('fn', 'fn-x'), |
| 689 | }[None if hash is None else bool(hash), # Force bool() if not None. |
| 690 | bool(eq), |
| 691 | bool(frozen)]['__hash__' in cls.__dict__] |
| 692 | # No need to call _set_new_attribute here, since we already know if |
| 693 | # we're overwriting a __hash__ or not. |
| 694 | if generate_hash == '': |
| 695 | # Do nothing. |
| 696 | pass |
| 697 | elif generate_hash == 'none': |
| 698 | cls.__hash__ = None |
| 699 | elif generate_hash in ('fn', 'fn-x'): |
| 700 | if generate_hash == 'fn' or auto_hash_test: |
| 701 | flds = [f for f in field_list |
| 702 | if (f.compare if f.hash is None else f.hash)] |
| 703 | cls.__hash__ = _hash_fn(flds) |
| 704 | else: |
| 705 | assert False, f"can't get here: {generate_hash}" |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 706 | |
| 707 | if not getattr(cls, '__doc__'): |
| 708 | # Create a class doc-string. |
| 709 | cls.__doc__ = (cls.__name__ + |
| 710 | str(inspect.signature(cls)).replace(' -> None', '')) |
| 711 | |
| 712 | return cls |
| 713 | |
| 714 | |
| 715 | # _cls should never be specified by keyword, so start it with an |
Raymond Hettinger | d55209d | 2018-01-10 20:56:41 -0800 | [diff] [blame] | 716 | # underscore. The presence of _cls is used to detect if this |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 717 | # decorator is being called with parameters or not. |
| 718 | def dataclass(_cls=None, *, init=True, repr=True, eq=True, order=False, |
| 719 | hash=None, frozen=False): |
| 720 | """Returns the same class as was passed in, with dunder methods |
| 721 | added based on the fields defined in the class. |
| 722 | |
| 723 | Examines PEP 526 __annotations__ to determine fields. |
| 724 | |
| 725 | If init is true, an __init__() method is added to the class. If |
| 726 | repr is true, a __repr__() method is added. If order is true, rich |
| 727 | comparison dunder methods are added. If hash is true, a __hash__() |
| 728 | method function is added. If frozen is true, fields may not be |
| 729 | assigned to after instance creation. |
| 730 | """ |
| 731 | |
| 732 | def wrap(cls): |
| 733 | return _process_class(cls, repr, eq, order, hash, init, frozen) |
| 734 | |
| 735 | # See if we're being called as @dataclass or @dataclass(). |
| 736 | if _cls is None: |
| 737 | # We're called with parens. |
| 738 | return wrap |
| 739 | |
| 740 | # We're called as @dataclass without parens. |
| 741 | return wrap(_cls) |
| 742 | |
| 743 | |
| 744 | def fields(class_or_instance): |
| 745 | """Return a tuple describing the fields of this dataclass. |
| 746 | |
| 747 | Accepts a dataclass or an instance of one. Tuple elements are of |
| 748 | type Field. |
| 749 | """ |
| 750 | |
| 751 | # Might it be worth caching this, per class? |
| 752 | try: |
| 753 | fields = getattr(class_or_instance, _MARKER) |
| 754 | except AttributeError: |
| 755 | raise TypeError('must be called with a dataclass type or instance') |
| 756 | |
Eric V. Smith | d138892 | 2018-01-07 14:30:17 -0500 | [diff] [blame] | 757 | # Exclude pseudo-fields. Note that fields is sorted by insertion |
| 758 | # order, so the order of the tuple is as the fields were defined. |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 759 | return tuple(f for f in fields.values() if f._field_type is _FIELD) |
| 760 | |
| 761 | |
Eric V. Smith | e7ba013 | 2018-01-06 12:41:53 -0500 | [diff] [blame] | 762 | def _is_dataclass_instance(obj): |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 763 | """Returns True if obj is an instance of a dataclass.""" |
| 764 | return not isinstance(obj, type) and hasattr(obj, _MARKER) |
| 765 | |
| 766 | |
Eric V. Smith | e7ba013 | 2018-01-06 12:41:53 -0500 | [diff] [blame] | 767 | def is_dataclass(obj): |
| 768 | """Returns True if obj is a dataclass or an instance of a |
| 769 | dataclass.""" |
| 770 | return hasattr(obj, _MARKER) |
| 771 | |
| 772 | |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 773 | def asdict(obj, *, dict_factory=dict): |
| 774 | """Return the fields of a dataclass instance as a new dictionary mapping |
| 775 | field names to field values. |
| 776 | |
| 777 | Example usage: |
| 778 | |
| 779 | @dataclass |
| 780 | class C: |
| 781 | x: int |
| 782 | y: int |
| 783 | |
| 784 | c = C(1, 2) |
| 785 | assert asdict(c) == {'x': 1, 'y': 2} |
| 786 | |
| 787 | If given, 'dict_factory' will be used instead of built-in dict. |
| 788 | The function applies recursively to field values that are |
| 789 | dataclass instances. This will also look into built-in containers: |
| 790 | tuples, lists, and dicts. |
| 791 | """ |
Eric V. Smith | e7ba013 | 2018-01-06 12:41:53 -0500 | [diff] [blame] | 792 | if not _is_dataclass_instance(obj): |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 793 | raise TypeError("asdict() should be called on dataclass instances") |
| 794 | return _asdict_inner(obj, dict_factory) |
| 795 | |
| 796 | def _asdict_inner(obj, dict_factory): |
Eric V. Smith | e7ba013 | 2018-01-06 12:41:53 -0500 | [diff] [blame] | 797 | if _is_dataclass_instance(obj): |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 798 | result = [] |
| 799 | for f in fields(obj): |
| 800 | value = _asdict_inner(getattr(obj, f.name), dict_factory) |
| 801 | result.append((f.name, value)) |
| 802 | return dict_factory(result) |
| 803 | elif isinstance(obj, (list, tuple)): |
| 804 | return type(obj)(_asdict_inner(v, dict_factory) for v in obj) |
| 805 | elif isinstance(obj, dict): |
| 806 | return type(obj)((_asdict_inner(k, dict_factory), _asdict_inner(v, dict_factory)) |
| 807 | for k, v in obj.items()) |
| 808 | else: |
| 809 | return deepcopy(obj) |
| 810 | |
| 811 | |
| 812 | def astuple(obj, *, tuple_factory=tuple): |
| 813 | """Return the fields of a dataclass instance as a new tuple of field values. |
| 814 | |
| 815 | Example usage:: |
| 816 | |
| 817 | @dataclass |
| 818 | class C: |
| 819 | x: int |
| 820 | y: int |
| 821 | |
| 822 | c = C(1, 2) |
Raymond Hettinger | d55209d | 2018-01-10 20:56:41 -0800 | [diff] [blame] | 823 | assert astuple(c) == (1, 2) |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 824 | |
| 825 | If given, 'tuple_factory' will be used instead of built-in tuple. |
| 826 | The function applies recursively to field values that are |
| 827 | dataclass instances. This will also look into built-in containers: |
| 828 | tuples, lists, and dicts. |
| 829 | """ |
| 830 | |
Eric V. Smith | e7ba013 | 2018-01-06 12:41:53 -0500 | [diff] [blame] | 831 | if not _is_dataclass_instance(obj): |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 832 | raise TypeError("astuple() should be called on dataclass instances") |
| 833 | return _astuple_inner(obj, tuple_factory) |
| 834 | |
| 835 | def _astuple_inner(obj, tuple_factory): |
Eric V. Smith | e7ba013 | 2018-01-06 12:41:53 -0500 | [diff] [blame] | 836 | if _is_dataclass_instance(obj): |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 837 | result = [] |
| 838 | for f in fields(obj): |
| 839 | value = _astuple_inner(getattr(obj, f.name), tuple_factory) |
| 840 | result.append(value) |
| 841 | return tuple_factory(result) |
| 842 | elif isinstance(obj, (list, tuple)): |
| 843 | return type(obj)(_astuple_inner(v, tuple_factory) for v in obj) |
| 844 | elif isinstance(obj, dict): |
| 845 | return type(obj)((_astuple_inner(k, tuple_factory), _astuple_inner(v, tuple_factory)) |
| 846 | for k, v in obj.items()) |
| 847 | else: |
| 848 | return deepcopy(obj) |
| 849 | |
| 850 | |
Eric V. Smith | d80b443 | 2018-01-06 17:09:58 -0500 | [diff] [blame] | 851 | def make_dataclass(cls_name, fields, *, bases=(), namespace=None, init=True, |
| 852 | repr=True, eq=True, order=False, hash=None, frozen=False): |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 853 | """Return a new dynamically created dataclass. |
| 854 | |
Eric V. Smith | ed7d429 | 2018-01-06 16:14:03 -0500 | [diff] [blame] | 855 | The dataclass name will be 'cls_name'. 'fields' is an iterable |
| 856 | of either (name), (name, type) or (name, type, Field) objects. If type is |
| 857 | omitted, use the string 'typing.Any'. Field objects are created by |
Eric V. Smith | d327ae6 | 2018-01-07 08:19:45 -0500 | [diff] [blame] | 858 | the equivalent of calling 'field(name, type [, Field-info])'. |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 859 | |
Raymond Hettinger | d55209d | 2018-01-10 20:56:41 -0800 | [diff] [blame] | 860 | C = make_dataclass('C', ['x', ('y', int), ('z', int, field(init=False))], bases=(Base,)) |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 861 | |
| 862 | is equivalent to: |
| 863 | |
| 864 | @dataclass |
| 865 | class C(Base): |
Raymond Hettinger | d55209d | 2018-01-10 20:56:41 -0800 | [diff] [blame] | 866 | x: 'typing.Any' |
| 867 | y: int |
| 868 | z: int = field(init=False) |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 869 | |
Raymond Hettinger | d55209d | 2018-01-10 20:56:41 -0800 | [diff] [blame] | 870 | For the bases and namespace parameters, see the builtin type() function. |
Eric V. Smith | d80b443 | 2018-01-06 17:09:58 -0500 | [diff] [blame] | 871 | |
| 872 | The parameters init, repr, eq, order, hash, and frozen are passed to |
| 873 | dataclass(). |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 874 | """ |
| 875 | |
| 876 | if namespace is None: |
| 877 | namespace = {} |
| 878 | else: |
| 879 | # Copy namespace since we're going to mutate it. |
| 880 | namespace = namespace.copy() |
| 881 | |
Eric V. Smith | d138892 | 2018-01-07 14:30:17 -0500 | [diff] [blame] | 882 | anns = {} |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 883 | for item in fields: |
Eric V. Smith | ed7d429 | 2018-01-06 16:14:03 -0500 | [diff] [blame] | 884 | if isinstance(item, str): |
| 885 | name = item |
| 886 | tp = 'typing.Any' |
| 887 | elif len(item) == 2: |
| 888 | name, tp, = item |
| 889 | elif len(item) == 3: |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 890 | name, tp, spec = item |
| 891 | namespace[name] = spec |
Eric V. Smith | ed7d429 | 2018-01-06 16:14:03 -0500 | [diff] [blame] | 892 | anns[name] = tp |
| 893 | |
| 894 | namespace['__annotations__'] = anns |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 895 | cls = type(cls_name, bases, namespace) |
Eric V. Smith | d80b443 | 2018-01-06 17:09:58 -0500 | [diff] [blame] | 896 | return dataclass(cls, init=init, repr=repr, eq=eq, order=order, |
| 897 | hash=hash, frozen=frozen) |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 898 | |
| 899 | def replace(obj, **changes): |
| 900 | """Return a new object replacing specified fields with new values. |
| 901 | |
| 902 | This is especially useful for frozen classes. Example usage: |
| 903 | |
| 904 | @dataclass(frozen=True) |
| 905 | class C: |
| 906 | x: int |
| 907 | y: int |
| 908 | |
| 909 | c = C(1, 2) |
| 910 | c1 = replace(c, x=3) |
| 911 | assert c1.x == 3 and c1.y == 2 |
| 912 | """ |
| 913 | |
| 914 | # We're going to mutate 'changes', but that's okay because it's a new |
| 915 | # dict, even if called with 'replace(obj, **my_changes)'. |
| 916 | |
Eric V. Smith | e7ba013 | 2018-01-06 12:41:53 -0500 | [diff] [blame] | 917 | if not _is_dataclass_instance(obj): |
Eric V. Smith | f0db54a | 2017-12-04 16:58:55 -0500 | [diff] [blame] | 918 | raise TypeError("replace() should be called on dataclass instances") |
| 919 | |
| 920 | # It's an error to have init=False fields in 'changes'. |
| 921 | # If a field is not in 'changes', read its value from the provided obj. |
| 922 | |
| 923 | for f in getattr(obj, _MARKER).values(): |
| 924 | if not f.init: |
| 925 | # Error if this field is specified in changes. |
| 926 | if f.name in changes: |
| 927 | raise ValueError(f'field {f.name} is declared with ' |
| 928 | 'init=False, it cannot be specified with ' |
| 929 | 'replace()') |
| 930 | continue |
| 931 | |
| 932 | if f.name not in changes: |
| 933 | changes[f.name] = getattr(obj, f.name) |
| 934 | |
| 935 | # Create the new object, which calls __init__() and __post_init__ |
| 936 | # (if defined), using all of the init fields we've added and/or |
| 937 | # left in 'changes'. |
| 938 | # If there are values supplied in changes that aren't fields, this |
| 939 | # will correctly raise a TypeError. |
| 940 | return obj.__class__(**changes) |