# (C) Copyright 2005-2022 Enthought, Inc., Austin, TX # All rights reserved. # # This software is provided without warranty under the terms of the BSD # license included in LICENSE.txt and may be redistributed only under # the conditions described in the aforementioned license. The license # is also available online at http://www.enthought.com/licenses/BSD.txt # # Thanks for using Enthought open source! """ Defines the 'core' traits for the Traits package. A trait is a type definition that can be used for normal Python object attributes, giving the attributes some additional characteristics: Initialization: Traits have predefined values that do not need to be explicitly initialized in the class constructor or elsewhere. Validation: Trait attributes have flexible, type-checked values. Delegation: Trait attributes' values can be delegated to other objects. Notification: Trait attributes can automatically notify interested parties when their values change. Visualization: Trait attributes can automatically construct (automatic or programmer-defined) user interfaces that allow their values to be edited or displayed) .. note:: 'trait' is a synonym for 'property', but is used instead of the word 'property' to differentiate it from the Python language 'property' feature. """ from types import FunctionType, MethodType import warnings from .constants import ( ComparisonMode, DefaultValue, TraitKind, ) from .ctrait import CTrait from .trait_errors import TraitError from .trait_base import ( SequenceTypes, TypeTypes, add_article, ) from .trait_converters import ( trait_cast, check_trait as try_trait_cast, ) from .trait_handler import TraitHandler from .trait_type import ( _infer_default_value_type, _read_only, _write_only, ) from .trait_handlers import ( TraitInstance, TraitFunction, TraitCoerceType, TraitCastType, TraitEnum, TraitCompound, TraitMap, _undefined_get, _undefined_set, ) from .trait_factory import ( TraitFactory, ) from .util.deprecated import deprecated # Constants NoneType = type(None) # Python 3's types does not include NoneType ConstantTypes = (NoneType, int, float, complex, str) PythonTypes = ( str, int, float, complex, list, tuple, dict, FunctionType, MethodType, type, NoneType, ) CallableTypes = (FunctionType, MethodType) TraitTypes = (TraitHandler, CTrait) DefaultValues = { str: "", int: 0, float: 0.0, complex: 0j, list: [], tuple: (), dict: {}, bool: False, } # This function is needed when unpickling historical pickles (pickles # created on versions of Traits prior to 6.0). It can be removed when # there's no longer any need to support pickles generated on older # versions of Traits. def __newobj__(cls, *args): """ Unpickles new-style objects. """ return cls.__new__(cls, *args) # --- 'instance' traits ------------------------------------------------------- class _InstanceArgs(object): def __init__(self, factory, args, kw): self.args = (factory,) + args self.kw = kw # --- 'creates a run-time default value' -------------------------------------- class Default(object): """ Generates a value the first time it is accessed. A Default object can be used anywhere a default trait value would normally be specified, to generate a default value dynamically. """ def __init__(self, func=None, args=(), kw=None): self.default_value = (func, args, kw) def Trait(*value_type, **metadata): """ Creates a trait definition. .. note:: The :func:`~.Trait` function is not recommended for use in new code, and may eventually be deprecated and removed. Consider using :class:`~.Union` instead. This function accepts a variety of forms of parameter lists: +-------------------+---------------+-------------------------------------+ | Format | Example | Description | +===================+===============+=====================================+ | Trait(*default*) | Trait(150.0) | The type of the trait is inferred | | | | from the type of the default value, | | | | which must be in *ConstantTypes*. | +-------------------+---------------+-------------------------------------+ | Trait(*default*, | Trait(None, | The trait accepts any of the | | *other1*, | 0, 1, 2, | enumerated values, with the first | | *other2*, ...) | 'many') | value being the default value. The | | | | values must be of types in | | | | *ConstantTypes*, but they need not | | | | be of the same type. The *default* | | | | value is not valid for assignment | | | | unless it is repeated later in the | | | | list. | +-------------------+---------------+-------------------------------------+ | Trait([*default*, | Trait([None, | Similar to the previous format, but | | *other1*, | 0, 1, 2, | takes an explicit list or a list | | *other2*, ...]) | 'many']) | variable. | +-------------------+---------------+-------------------------------------+ | Trait(*type*) | Trait(Int) | The *type* parameter must be a name | | | | of a Python type (see | | | | *PythonTypes*). Assigned values | | | | must be of exactly the specified | | | | type; no casting or coercion is | | | | performed. The default value is the | | | | appropriate form of zero, False, | | | | or emtpy string, set or sequence. | +-------------------+---------------+-------------------------------------+ | Trait(*class*) |:: | Values must be instances of *class* | | | | or of a subclass of *class*. The | | | class MyClass:| default value is None, but None | | | pass | cannot be assigned as a value. | | | foo = Trait( | | | | MyClass) | | +-------------------+---------------+-------------------------------------+ | Trait(None, |:: | Similar to the previous format, but | | *class*) | | None *can* be assigned as a value. | | | class MyClass:| | | | pass | | | | foo = Trait( | | | | None, MyClass)| | +-------------------+---------------+-------------------------------------+ | Trait(*instance*) |:: | Values must be instances of the | | | | same class as *instance*, or of a | | | class MyClass:| subclass of that class. The | | | pass | specified instance is the default | | | i = MyClass() | value. | | | foo = | | | | Trait(i) | | +-------------------+---------------+-------------------------------------+ | Trait(*handler*) | Trait( | Assignment to this trait is | | | TraitEnum ) | validated by an object derived from | | | | **traits.TraitHandler**. | +-------------------+---------------+-------------------------------------+ | Trait(*default*, | Trait(0.0, 0.0| This is the most general form of | | { *type* | | 'stuff', | the function. The notation: | | *constant* | | TupleType) | ``{...|...|...}+`` means a list of | | *dict* | *class* || | one or more of any of the items | | *function* | | | listed between the braces. Thus, the| | *handler* | | | most general form of the function | | *trait* }+ ) | | consists of a default value, | | | | followed by one or more of several | | | | possible items. A trait defined by | | | | multiple items is called a | | | | "compound" trait. | +-------------------+---------------+-------------------------------------+ All forms of the Trait function accept both predefined and arbitrary keyword arguments. The value of each keyword argument becomes bound to the resulting trait object as the value of an attribute having the same name as the keyword. This feature lets you associate metadata with a trait. The following predefined keywords are accepted: desc : str Describes the intended meaning of the trait. It is used in exception messages and fly-over help in user interfaces. label : str Provides a human-readable name for the trait. It is used to label user interface editors for traits. editor : traits.api.Editor Instance of a subclass Editor object to use when creating a user interface editor for the trait. See the "Traits UI User Guide" for more information on trait editors. comparison_mode : int Indicates when trait change notifications should be generated based upon the result of comparing the old and new values of a trait assignment. Possible values come from the ``ComparisonMode`` enum: * 0 (none): The values are not compared and a trait change notification is generated on each assignment. * 1 (identity): A trait change notification is generated if the old and new values are not the same object. * 2 (equality): A trait change notification is generated if the old and new values are not equal using Python's standard equality testing. This is the default. """ return _TraitMaker(*value_type, **metadata).as_ctrait() class _TraitMaker(object): # Ctrait type map for special trait types: type_map = {"event": TraitKind.event, "constant": TraitKind.constant} def __init__(self, *value_type, **metadata): metadata.setdefault("type", "trait") self.define(*value_type, **metadata) def define(self, *value_type, **metadata): """ Define the trait. """ default_value_type = DefaultValue.unspecified default_value = handler = clone = None if len(value_type) > 0: default_value = value_type[0] value_type = value_type[1:] if (len(value_type) == 0) and ( type(default_value) in SequenceTypes ): default_value, value_type = default_value[0], default_value if len(value_type) == 0: default_value = try_trait_cast(default_value) if default_value in PythonTypes: handler = TraitCoerceType(default_value) default_value = DefaultValues.get(default_value) elif isinstance(default_value, CTrait): clone = default_value default_value_type, default_value = clone.default_value() metadata["type"] = clone.type elif isinstance(default_value, TraitHandler): handler = default_value default_value = None else: typeValue = type(default_value) if typeValue in TypeTypes: handler = TraitCastType(typeValue) else: metadata.setdefault( "instance_handler", "_instance_changed_handler" ) handler = TraitInstance(default_value) if default_value is handler.aClass: default_value = DefaultValues.get(default_value) else: enum = [] other = [] map = {} self.do_list(value_type, enum, map, other) if ((len(enum) == 1) and (enum[0] is None)) and ( (len(other) == 1) and isinstance(other[0], TraitInstance) ): enum = [] other[0].allow_none() metadata.setdefault( "instance_handler", "_instance_changed_handler" ) if len(enum) > 0: if ((len(map) + len(other)) == 0) and ( default_value not in enum ): enum.insert(0, default_value) other.append(TraitEnum(enum)) if len(map) > 0: other.append(TraitMap(map)) if len(other) == 0: handler = TraitHandler() elif len(other) == 1: handler = other[0] if isinstance(handler, CTrait): clone, handler = handler, None metadata["type"] = clone.type elif isinstance(handler, TraitInstance): metadata.setdefault( "instance_handler", "_instance_changed_handler" ) if default_value is None: handler.allow_none() elif isinstance(default_value, _InstanceArgs): default_value_type = ( DefaultValue.callable_and_args ) default_value = ( handler.create_default_value, default_value.args, default_value.kw, ) elif (len(enum) == 0) and (len(map) == 0): aClass = handler.aClass typeValue = type(default_value) if typeValue is dict: default_value_type = ( DefaultValue.callable_and_args ) default_value = (aClass, (), default_value) elif not isinstance(default_value, aClass): if typeValue is not tuple: default_value = (default_value,) default_value_type = ( DefaultValue.callable_and_args ) default_value = (aClass, default_value, None) else: for i, item in enumerate(other): if isinstance(item, CTrait): if item.type != "trait": raise TraitError( "Cannot create a complex " "trait containing %s trait." % add_article(item.type) ) handler = item.handler if handler is None: break other[i] = handler else: handler = TraitCompound(other) # Save the results: self.handler = handler self.clone = clone if default_value_type < 0: if isinstance(default_value, Default): default_value_type = DefaultValue.callable_and_args default_value = default_value.default_value else: if (handler is None) and (clone is not None): handler = clone.handler if handler is not None: default_value_type = handler.default_value_type if default_value_type < 0: try: default_value = handler.validate( None, "", default_value ) except: pass if default_value_type < 0: default_value_type = _infer_default_value_type( default_value ) self.default_value_type = default_value_type self.default_value = default_value self.metadata = metadata.copy() def do_list(self, list, enum, map, other): """ Determine the correct TraitHandler for each item in a list. """ for item in list: if item in PythonTypes: other.append(TraitCoerceType(item)) else: item = try_trait_cast(item) typeItem = type(item) if typeItem in ConstantTypes: enum.append(item) elif typeItem in SequenceTypes: self.do_list(item, enum, map, other) elif typeItem is dict: map.update(item) elif typeItem in CallableTypes: other.append(TraitFunction(item)) elif isinstance(item, TraitTypes): other.append(item) else: other.append(TraitInstance(item)) def as_ctrait(self): """ Return a properly initialized 'CTrait' instance. """ metadata = self.metadata trait = CTrait( self.type_map.get(metadata.get("type"), TraitKind.trait)) clone = self.clone if clone is not None: trait.clone(clone) if clone.__dict__ is not None: trait.__dict__ = clone.__dict__.copy() trait.set_default_value(self.default_value_type, self.default_value) handler = self.handler if handler is not None: trait.handler = handler validate = getattr(handler, "fast_validate", None) if validate is None: validate = handler.validate trait.set_validate(validate) post_setattr = getattr(handler, "post_setattr", None) if post_setattr is not None: trait.post_setattr = post_setattr trait.is_mapped = handler.is_mapped rich_compare = metadata.get("rich_compare") if rich_compare is not None: # Ref: enthought/traits#602 warnings.warn( "The 'rich_compare' metadata has been deprecated. Please " "use the 'comparison_mode' metadata instead. In a future " "release, rich_compare will have no effect.", DeprecationWarning, stacklevel=4, ) if rich_compare: trait.comparison_mode = ComparisonMode.equality else: trait.comparison_mode = ComparisonMode.identity comparison_mode = metadata.pop("comparison_mode", None) if comparison_mode is not None: trait.comparison_mode = comparison_mode if len(metadata) > 0: if trait.__dict__ is None: trait.__dict__ = metadata else: trait.__dict__.update(metadata) return trait def Property( fget=None, fset=None, fvalidate=None, force=False, handler=None, trait=None, **metadata ): """ Returns a trait whose value is a Python property. If no getter, setter or validate functions are specified (and **force** is not True), it is assumed that they are defined elsewhere on the class whose attribute this trait is assigned to. For example:: class Bar(HasTraits): # A float traits Property that should be always positive. foo = Property(Float) # Shadow trait attribute _foo = Float def _set_foo(self,x): self._foo = x def _validate_foo(self, x): if x <= 0: raise TraitError( 'foo property should be a positive number') return x def _get_foo(self): return self._foo You can use the **observe** metadata attribute to indicate that the property depends on the value of another trait. The value of **observe** follows the same signature as the **expression** parameter in ``HasTraits.observe``. The property will fire a trait change notification if any of the traits specified by **observe** change. For example:: class Wheel(Part): axle = Instance(Axle) position = Property(observe='axle.chassis.position') For details of the extended trait name syntax, refer to the observe() method of the HasTraits class. Parameters ---------- fget : function The "getter" function for the property. fset : function The "setter" function for the property. fvalidate : function The validation function for the property. The method should return the value to set or raise TraitError if the new value is not valid. force : bool Indicates whether to use only the function definitions specified by **fget** and **fset**, and not look elsewhere on the class. handler : function A trait handler function for the trait. trait : Trait or value A trait definition or a value that can be converted to a trait that constrains the values of the property trait. """ metadata["type"] = "property" # If no parameters specified, must be a forward reference (if not forced): if (not force) and (fset is None): sum = ( (fget is not None) + (fvalidate is not None) + (trait is not None) ) if sum <= 1: if sum == 0: return ForwardProperty(metadata) handler = None if fget is not None: trait = fget if trait is not None: trait = trait_cast(trait) if trait is not None: fvalidate = handler = trait.handler if fvalidate is not None: fvalidate = handler.validate if (fvalidate is not None) or (trait is not None): if "editor" not in metadata: if (trait is not None) and (trait.editor is not None): metadata["editor"] = trait.editor return ForwardProperty(metadata, fvalidate, handler) if fget is None: metadata["transient"] = True if fset is None: fget = _undefined_get fset = _undefined_set else: fget = _write_only elif fset is None: fset = _read_only metadata["transient"] = True if trait is not None: trait = trait_cast(trait) handler = trait.handler if (fvalidate is None) and (handler is not None): fvalidate = handler.validate if ("editor" not in metadata) and (trait.editor is not None): metadata["editor"] = trait.editor metadata.setdefault("depends_on", getattr(fget, "depends_on", None)) if getattr(fget, "cached_property", False): metadata.setdefault("cached", True) trait = CTrait(TraitKind.property) trait.__dict__ = metadata.copy() trait.property_fields = (fget, fset, fvalidate) trait.handler = handler return trait Property = TraitFactory(Property) class ForwardProperty(object): """ Used to implement Property traits where accessor functions are defined implicitly on the class. """ def __init__(self, metadata, validate=None, handler=None): self.metadata = metadata.copy() self.validate = validate self.handler = handler # Predefined, reusable trait instances # Generic trait with 'object' behavior: generic_trait = CTrait(TraitKind.generic) # User interface related color and font traits @deprecated("'Color' in 'traits' package has been deprecated. " "Use 'Color' from 'traitsui' package instead.") def Color(*args, **metadata): """ Returns a trait whose value must be a GUI toolkit-specific color. .. deprecated:: 6.1.0 ``Color`` trait in this package will be removed in the future. It is replaced by ``Color`` trait in TraitsUI package. """ from traitsui.toolkit_traits import ColorTrait return ColorTrait(*args, **metadata) Color = TraitFactory(Color) @deprecated("'RGBColor' in 'traits' package has been deprecated. " "Use 'RGBColor' from 'traitsui' package instead.") def RGBColor(*args, **metadata): """ Returns a trait whose value must be a GUI toolkit-specific RGB-based color. .. deprecated:: 6.1.0 ``RGBColor`` trait in this package will be removed in the future. It is replaced by ``RGBColor`` trait in TraitsUI package. """ from traitsui.toolkit_traits import RGBColorTrait return RGBColorTrait(*args, **metadata) RGBColor = TraitFactory(RGBColor) @deprecated("'Font' in 'traits' package has been deprecated. " "Use 'Font' from 'traitsui' package instead.") def Font(*args, **metadata): """ Returns a trait whose value must be a GUI toolkit-specific font. .. deprecated:: 6.1.0 ``Font`` trait in this package will be removed in the future. It is replaced by ``Font`` trait in TraitsUI package. """ from traitsui.toolkit_traits import FontTrait return FontTrait(*args, **metadata) Font = TraitFactory(Font)