777 lines
28 KiB
Python
777 lines
28 KiB
Python
import sys
|
|
import types
|
|
from copy import deepcopy
|
|
import collections
|
|
import inspect
|
|
|
|
__all__ = ['dataclass',
|
|
'field',
|
|
'FrozenInstanceError',
|
|
'InitVar',
|
|
|
|
# Helper functions.
|
|
'fields',
|
|
'asdict',
|
|
'astuple',
|
|
'make_dataclass',
|
|
'replace',
|
|
]
|
|
|
|
# Raised when an attempt is made to modify a frozen class.
|
|
class FrozenInstanceError(AttributeError): pass
|
|
|
|
# A sentinel object for default values to signal that a
|
|
# default-factory will be used.
|
|
# This is given a nice repr() which will appear in the function
|
|
# signature of dataclasses' constructors.
|
|
class _HAS_DEFAULT_FACTORY_CLASS:
|
|
def __repr__(self):
|
|
return '<factory>'
|
|
_HAS_DEFAULT_FACTORY = _HAS_DEFAULT_FACTORY_CLASS()
|
|
|
|
# A sentinel object to detect if a parameter is supplied or not.
|
|
class _MISSING_FACTORY:
|
|
def __repr__(self):
|
|
return '<missing>'
|
|
_MISSING = _MISSING_FACTORY()
|
|
|
|
# Since most per-field metadata will be unused, create an empty
|
|
# read-only proxy that can be shared among all fields.
|
|
_EMPTY_METADATA = types.MappingProxyType({})
|
|
|
|
# Markers for the various kinds of fields and pseudo-fields.
|
|
_FIELD = object() # An actual field.
|
|
_FIELD_CLASSVAR = object() # Not a field, but a ClassVar.
|
|
_FIELD_INITVAR = object() # Not a field, but an InitVar.
|
|
|
|
# The name of an attribute on the class where we store the Field
|
|
# objects. Also used to check if a class is a Data Class.
|
|
_MARKER = '__dataclass_fields__'
|
|
|
|
# The name of the function, that if it exists, is called at the end of
|
|
# __init__.
|
|
_POST_INIT_NAME = '__post_init__'
|
|
|
|
|
|
class _InitVarMeta(type):
|
|
def __getitem__(self, params):
|
|
return self
|
|
|
|
class InitVar(metaclass=_InitVarMeta):
|
|
pass
|
|
|
|
|
|
# Instances of Field are only ever created from within this module,
|
|
# and only from the field() function, although Field instances are
|
|
# exposed externally as (conceptually) read-only objects.
|
|
# name and type are filled in after the fact, not in __init__. They're
|
|
# not known at the time this class is instantiated, but it's
|
|
# convenient if they're available later.
|
|
# When cls._MARKER is filled in with a list of Field objects, the name
|
|
# and type fields will have been populated.
|
|
class Field:
|
|
__slots__ = ('name',
|
|
'type',
|
|
'default',
|
|
'default_factory',
|
|
'repr',
|
|
'hash',
|
|
'init',
|
|
'compare',
|
|
'metadata',
|
|
'_field_type', # Private: not to be used by user code.
|
|
)
|
|
|
|
def __init__(self, default, default_factory, init, repr, hash, compare,
|
|
metadata):
|
|
self.name = None
|
|
self.type = None
|
|
self.default = default
|
|
self.default_factory = default_factory
|
|
self.init = init
|
|
self.repr = repr
|
|
self.hash = hash
|
|
self.compare = compare
|
|
self.metadata = (_EMPTY_METADATA
|
|
if metadata is None or len(metadata) == 0 else
|
|
types.MappingProxyType(metadata))
|
|
self._field_type = None
|
|
|
|
def __repr__(self):
|
|
return ('Field('
|
|
f'name={self.name!r},'
|
|
f'type={self.type},'
|
|
f'default={self.default},'
|
|
f'default_factory={self.default_factory},'
|
|
f'init={self.init},'
|
|
f'repr={self.repr},'
|
|
f'hash={self.hash},'
|
|
f'compare={self.compare},'
|
|
f'metadata={self.metadata}'
|
|
')')
|
|
|
|
|
|
# This function is used instead of exposing Field creation directly,
|
|
# so that a type checker can be told (via overloads) that this is a
|
|
# function whose type depends on its parameters.
|
|
def field(*, default=_MISSING, default_factory=_MISSING, init=True, repr=True,
|
|
hash=None, compare=True, metadata=None):
|
|
"""Return an object to identify dataclass fields.
|
|
|
|
default is the default value of the field. default_factory is a
|
|
0-argument function called to initialize a field's value. If init
|
|
is True, the field will be a parameter to the class's __init__()
|
|
function. If repr is True, the field will be included in the
|
|
object's repr(). If hash is True, the field will be included in
|
|
the object's hash(). If compare is True, the field will be used in
|
|
comparison functions. metadata, if specified, must be a mapping
|
|
which is stored but not otherwise examined by dataclass.
|
|
|
|
It is an error to specify both default and default_factory.
|
|
"""
|
|
|
|
if default is not _MISSING and default_factory is not _MISSING:
|
|
raise ValueError('cannot specify both default and default_factory')
|
|
return Field(default, default_factory, init, repr, hash, compare,
|
|
metadata)
|
|
|
|
|
|
def _tuple_str(obj_name, fields):
|
|
# Return a string representing each field of obj_name as a tuple
|
|
# member. So, if fields is ['x', 'y'] and obj_name is "self",
|
|
# return "(self.x,self.y)".
|
|
|
|
# Special case for the 0-tuple.
|
|
if len(fields) == 0:
|
|
return '()'
|
|
# Note the trailing comma, needed if this turns out to be a 1-tuple.
|
|
return f'({",".join([f"{obj_name}.{f.name}" for f in fields])},)'
|
|
|
|
|
|
def _create_fn(name, args, body, globals=None, locals=None,
|
|
return_type=_MISSING):
|
|
# Note that we mutate locals when exec() is called. Caller beware!
|
|
if locals is None:
|
|
locals = {}
|
|
return_annotation = ''
|
|
if return_type is not _MISSING:
|
|
locals['_return_type'] = return_type
|
|
return_annotation = '->_return_type'
|
|
args = ','.join(args)
|
|
body = '\n'.join(f' {b}' for b in body)
|
|
|
|
txt = f'def {name}({args}){return_annotation}:\n{body}'
|
|
|
|
exec(txt, globals, locals)
|
|
return locals[name]
|
|
|
|
|
|
def _field_assign(frozen, name, value, self_name):
|
|
# If we're a frozen class, then assign to our fields in __init__
|
|
# via object.__setattr__. Otherwise, just use a simple
|
|
# assignment.
|
|
# self_name is what "self" is called in this function: don't
|
|
# hard-code "self", since that might be a field name.
|
|
if frozen:
|
|
return f'object.__setattr__({self_name},{name!r},{value})'
|
|
return f'{self_name}.{name}={value}'
|
|
|
|
|
|
def _field_init(f, frozen, globals, self_name):
|
|
# Return the text of the line in the body of __init__ that will
|
|
# initialize this field.
|
|
|
|
default_name = f'_dflt_{f.name}'
|
|
if f.default_factory is not _MISSING:
|
|
if f.init:
|
|
# This field has a default factory. If a parameter is
|
|
# given, use it. If not, call the factory.
|
|
globals[default_name] = f.default_factory
|
|
value = (f'{default_name}() '
|
|
f'if {f.name} is _HAS_DEFAULT_FACTORY '
|
|
f'else {f.name}')
|
|
else:
|
|
# This is a field that's not in the __init__ params, but
|
|
# has a default factory function. It needs to be
|
|
# initialized here by calling the factory function,
|
|
# because there's no other way to initialize it.
|
|
|
|
# For a field initialized with a default=defaultvalue, the
|
|
# class dict just has the default value
|
|
# (cls.fieldname=defaultvalue). But that won't work for a
|
|
# default factory, the factory must be called in __init__
|
|
# and we must assign that to self.fieldname. We can't
|
|
# fall back to the class dict's value, both because it's
|
|
# not set, and because it might be different per-class
|
|
# (which, after all, is why we have a factory function!).
|
|
|
|
globals[default_name] = f.default_factory
|
|
value = f'{default_name}()'
|
|
else:
|
|
# No default factory.
|
|
if f.init:
|
|
if f.default is _MISSING:
|
|
# There's no default, just do an assignment.
|
|
value = f.name
|
|
elif f.default is not _MISSING:
|
|
globals[default_name] = f.default
|
|
value = f.name
|
|
else:
|
|
# This field does not need initialization. Signify that to
|
|
# the caller by returning None.
|
|
return None
|
|
|
|
# Only test this now, so that we can create variables for the
|
|
# default. However, return None to signify that we're not going
|
|
# to actually do the assignment statement for InitVars.
|
|
if f._field_type == _FIELD_INITVAR:
|
|
return None
|
|
|
|
# Now, actually generate the field assignment.
|
|
return _field_assign(frozen, f.name, value, self_name)
|
|
|
|
|
|
def _init_param(f):
|
|
# Return the __init__ parameter string for this field.
|
|
# For example, the equivalent of 'x:int=3' (except instead of 'int',
|
|
# reference a variable set to int, and instead of '3', reference a
|
|
# variable set to 3).
|
|
if f.default is _MISSING and f.default_factory is _MISSING:
|
|
# There's no default, and no default_factory, just
|
|
# output the variable name and type.
|
|
default = ''
|
|
elif f.default is not _MISSING:
|
|
# There's a default, this will be the name that's used to look it up.
|
|
default = f'=_dflt_{f.name}'
|
|
elif f.default_factory is not _MISSING:
|
|
# There's a factory function. Set a marker.
|
|
default = '=_HAS_DEFAULT_FACTORY'
|
|
return f'{f.name}:_type_{f.name}{default}'
|
|
|
|
|
|
def _init_fn(fields, frozen, has_post_init, self_name):
|
|
# fields contains both real fields and InitVar pseudo-fields.
|
|
|
|
# Make sure we don't have fields without defaults following fields
|
|
# with defaults. This actually would be caught when exec-ing the
|
|
# function source code, but catching it here gives a better error
|
|
# message, and future-proofs us in case we build up the function
|
|
# using ast.
|
|
seen_default = False
|
|
for f in fields:
|
|
# Only consider fields in the __init__ call.
|
|
if f.init:
|
|
if not (f.default is _MISSING and f.default_factory is _MISSING):
|
|
seen_default = True
|
|
elif seen_default:
|
|
raise TypeError(f'non-default argument {f.name!r} '
|
|
'follows default argument')
|
|
|
|
globals = {'_MISSING': _MISSING,
|
|
'_HAS_DEFAULT_FACTORY': _HAS_DEFAULT_FACTORY}
|
|
|
|
body_lines = []
|
|
for f in fields:
|
|
# Do not initialize the pseudo-fields, only the real ones.
|
|
line = _field_init(f, frozen, globals, self_name)
|
|
if line is not None:
|
|
# line is None means that this field doesn't require
|
|
# initialization. Just skip it.
|
|
body_lines.append(line)
|
|
|
|
# Does this class have a post-init function?
|
|
if has_post_init:
|
|
params_str = ','.join(f.name for f in fields
|
|
if f._field_type is _FIELD_INITVAR)
|
|
body_lines += [f'{self_name}.{_POST_INIT_NAME}({params_str})']
|
|
|
|
# If no body lines, use 'pass'.
|
|
if len(body_lines) == 0:
|
|
body_lines = ['pass']
|
|
|
|
locals = {f'_type_{f.name}': f.type for f in fields}
|
|
return _create_fn('__init__',
|
|
[self_name] +[_init_param(f) for f in fields if f.init],
|
|
body_lines,
|
|
locals=locals,
|
|
globals=globals,
|
|
return_type=None)
|
|
|
|
|
|
def _repr_fn(fields):
|
|
return _create_fn('__repr__',
|
|
['self'],
|
|
['return self.__class__.__qualname__ + f"(' +
|
|
', '.join([f"{f.name}={{self.{f.name}!r}}"
|
|
for f in fields]) +
|
|
')"'])
|
|
|
|
|
|
def _frozen_setattr(self, name, value):
|
|
raise FrozenInstanceError(f'cannot assign to field {name!r}')
|
|
|
|
|
|
def _frozen_delattr(self, name):
|
|
raise FrozenInstanceError(f'cannot delete field {name!r}')
|
|
|
|
|
|
def _cmp_fn(name, op, self_tuple, other_tuple):
|
|
# Create a comparison function. If the fields in the object are
|
|
# named 'x' and 'y', then self_tuple is the string
|
|
# '(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 _set_eq_fns(cls, fields):
|
|
# Create and set the equality comparison methods on cls.
|
|
# Pre-compute self_tuple and other_tuple, then re-use them for
|
|
# each function.
|
|
self_tuple = _tuple_str('self', fields)
|
|
other_tuple = _tuple_str('other', fields)
|
|
for name, op in [('__eq__', '=='),
|
|
('__ne__', '!='),
|
|
]:
|
|
_set_attribute(cls, name, _cmp_fn(name, op, self_tuple, other_tuple))
|
|
|
|
|
|
def _set_order_fns(cls, fields):
|
|
# Create and set the ordering methods on cls.
|
|
# Pre-compute self_tuple and other_tuple, then re-use them for
|
|
# each function.
|
|
self_tuple = _tuple_str('self', fields)
|
|
other_tuple = _tuple_str('other', fields)
|
|
for name, op in [('__lt__', '<'),
|
|
('__le__', '<='),
|
|
('__gt__', '>'),
|
|
('__ge__', '>='),
|
|
]:
|
|
_set_attribute(cls, name, _cmp_fn(name, op, self_tuple, other_tuple))
|
|
|
|
|
|
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:
|
|
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._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 _find_fields(cls):
|
|
# Return a list of Field objects, in order, for this class (and no
|
|
# base classes). Fields are found from __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 deal with later.
|
|
|
|
annotations = getattr(cls, '__annotations__', {})
|
|
|
|
return [_get_field(cls, a_name, a_type)
|
|
for a_name, a_type in annotations.items()]
|
|
|
|
|
|
def _set_attribute(cls, name, value):
|
|
# Raise TypeError if an attribute by this name already exists.
|
|
if name in cls.__dict__:
|
|
raise TypeError(f'Cannot overwrite attribute {name} '
|
|
f'in {cls.__name__}')
|
|
setattr(cls, name, value)
|
|
|
|
|
|
def _process_class(cls, repr, eq, order, hash, init, frozen):
|
|
# Use an OrderedDict because:
|
|
# - Order matters!
|
|
# - Derived class fields overwrite base class fields, but the
|
|
# order is defined by the base class, which is found first.
|
|
fields = collections.OrderedDict()
|
|
|
|
# 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.
|
|
for b in cls.__mro__[-1:0:-1]:
|
|
# Only process classes that have been processed by our
|
|
# decorator. That is, they have a _MARKER attribute.
|
|
base_fields = getattr(b, _MARKER, None)
|
|
if base_fields:
|
|
for f in base_fields.values():
|
|
fields[f.name] = f
|
|
|
|
# Now find fields in our class. While doing so, validate some
|
|
# things, and set the default values (as class attributes)
|
|
# where we can.
|
|
for f in _find_fields(cls):
|
|
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)
|
|
|
|
# Remember all of the fields on our class (including bases). This
|
|
# marks this class as being a dataclass.
|
|
setattr(cls, _MARKER, fields)
|
|
|
|
# We also need to check if a parent class is frozen: frozen has to
|
|
# be inherited down.
|
|
is_frozen = frozen or cls.__setattr__ is _frozen_setattr
|
|
|
|
# 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).
|
|
_set_attribute(cls, '__init__',
|
|
_init_fn(list(filter(lambda f: f._field_type
|
|
in (_FIELD, _FIELD_INITVAR),
|
|
fields.values())),
|
|
is_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 = list(filter(lambda f: f._field_type is _FIELD,
|
|
fields.values()))
|
|
|
|
if repr:
|
|
_set_attribute(cls, '__repr__',
|
|
_repr_fn(list(filter(lambda f: f.repr, field_list))))
|
|
|
|
if is_frozen:
|
|
_set_attribute(cls, '__setattr__', _frozen_setattr)
|
|
_set_attribute(cls, '__delattr__', _frozen_delattr)
|
|
|
|
generate_hash = False
|
|
if hash is None:
|
|
if eq and frozen:
|
|
# Generate a hash function.
|
|
generate_hash = True
|
|
elif eq and not frozen:
|
|
# Not hashable.
|
|
_set_attribute(cls, '__hash__', None)
|
|
elif not eq:
|
|
# Otherwise, use the base class definition of hash(). That is,
|
|
# don't set anything on this class.
|
|
pass
|
|
else:
|
|
assert "can't get here"
|
|
else:
|
|
generate_hash = hash
|
|
if generate_hash:
|
|
_set_attribute(cls, '__hash__',
|
|
_hash_fn(list(filter(lambda f: f.compare
|
|
if f.hash is None
|
|
else f.hash,
|
|
field_list))))
|
|
|
|
if eq:
|
|
# Create and __eq__ and __ne__ methods.
|
|
_set_eq_fns(cls, list(filter(lambda f: f.compare, field_list)))
|
|
|
|
if order:
|
|
# Create and __lt__, __le__, __gt__, and __ge__ methods.
|
|
# Create and set the comparison functions.
|
|
_set_order_fns(cls, list(filter(lambda f: f.compare, 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 presense 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):
|
|
"""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 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)
|
|
|
|
# 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, _MARKER)
|
|
except AttributeError:
|
|
raise TypeError('must be called with a dataclass type or instance')
|
|
|
|
# Exclude pseudo-fields.
|
|
return tuple(f for f in fields.values() if f._field_type is _FIELD)
|
|
|
|
|
|
def _isdataclass(obj):
|
|
"""Returns True if obj is an instance of a dataclass."""
|
|
return not isinstance(obj, type) and hasattr(obj, _MARKER)
|
|
|
|
|
|
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 _isdataclass(obj):
|
|
raise TypeError("asdict() should be called on dataclass instances")
|
|
return _asdict_inner(obj, dict_factory)
|
|
|
|
def _asdict_inner(obj, dict_factory):
|
|
if _isdataclass(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 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 asdtuple(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 _isdataclass(obj):
|
|
raise TypeError("astuple() should be called on dataclass instances")
|
|
return _astuple_inner(obj, tuple_factory)
|
|
|
|
def _astuple_inner(obj, tuple_factory):
|
|
if _isdataclass(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 deepcopy(obj)
|
|
|
|
|
|
def make_dataclass(cls_name, fields, *, bases=(), namespace=None):
|
|
"""Return a new dynamically created dataclass.
|
|
|
|
The dataclass name will be 'cls_name'. 'fields' is an interable
|
|
of either (name, type) or (name, type, Field) objects. Field
|
|
objects are created by calling 'field(name, type [, Field])'.
|
|
|
|
C = make_class('C', [('a', int', ('b', int, Field(init=False))], bases=Base)
|
|
|
|
is equivalent to:
|
|
|
|
@dataclass
|
|
class C(Base):
|
|
a: int
|
|
b: int = field(init=False)
|
|
|
|
For the bases and namespace paremeters, see the builtin type() function.
|
|
"""
|
|
|
|
if namespace is None:
|
|
namespace = {}
|
|
else:
|
|
# Copy namespace since we're going to mutate it.
|
|
namespace = namespace.copy()
|
|
|
|
anns = collections.OrderedDict((name, tp) for name, tp, *_ in fields)
|
|
namespace['__annotations__'] = anns
|
|
for item in fields:
|
|
if len(item) == 3:
|
|
name, tp, spec = item
|
|
namespace[name] = spec
|
|
cls = type(cls_name, bases, namespace)
|
|
return dataclass(cls)
|
|
|
|
|
|
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 _isdataclass(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, _MARKER).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)
|