Module ocd.prop
Automatic property creation.
- Provides some functions to make getter and setter functions for various purposes.
- Provides Metaclass for Mixin classes that can be used to automatically create properties (with default values if given).
Expand source code
"""Automatic property creation.
* Provides some functions to make getter and setter functions for
various purposes.
* Provides Metaclass for Mixin classes that can be used to
automatically create properties (with default values if given).
"""
__author__ = 'Md Jahidul Hamid <jahidulhamid@yahoo.com>'
__copyright__ = 'Copyright © Md Jahidul Hamid <https://github.com/neurobin/>'
__license__ = '[BSD](http://www.opensource.org/licenses/bsd-license.php)'
__version__ = '0.0.4'
from abc import ABCMeta
from copy import deepcopy
from ocd import Void
from ocd.unro import ClassReadonly, Unro
from ocd import abc
def make_fget(name, var_name, default=Void):
"""Return a function compatible with `property()` function `fget`
parameter
Args:
name (str): name of the property
var_name (str): internal variable name
default (any, optional): Default value. Defaults to Void.
Raises:
AttributeError: when fails to get the attribute
Returns:
function: A getter function
"""
def fget(self):
v = getattr(self, var_name, default)
if v is Void:
raise AttributeError("Property '%s' is not set yet for %r"
% (name, self,))
return v
return fget
def make_fget_const(name, v):
"""Make a getter for `property()` function `fget` param that
returns a constant value.
Args:
name (str): name of the property
v (any): the constant value of the property
Raises:
AttributeError: when the constant value is Void
Returns:
function: A getter function
"""
def fget(self):
if v is Void:
raise AttributeError("The value of property '%s' is non-existent "
"for %r. It can neither be read nor be "
"written." % (name, self,))
return v
return fget
def make_fset(name, var_name):
"""Make a setter for `property()`'s `fset` param for property name
and internal variable name
Args:
name (str): property name
var_name (str): internal variable name
Returns:
function: A setter function
"""
def fset(self, value):
setattr(self, var_name, value)
return fset
def make_nofset(name):
"""Make a setter for `property()`'s `fset` param that raises
`AttributeError`
Args:
name (str): property name
Raises:
AttributeError: always raises exception
Returns:
function: A setter function
"""
def fset(self, value):
raise AttributeError("'%s' is a readonly property for %r"
% (name, self,))
return fset
def make_fdel(name, var_name=None):
"""Make a deleter for `property()`'s `fdel` param
Args:
name (str): property name
var_name (str): internal variable name.
Returns:
function: A deleter function
"""
def fdel(self):
if var_name:
delattr(self, var_name)
else:
raise AttributeError("Constant readonly property '%s' can not be "
"deleted by %r" % (name, self,))
return fdel
def make_nofdel(name):
"""Make a deleter for `property()`'s `fdel` param that raises
`AttributeError`
Args:
name (str): property name
Raises:
AttributeError: always raises exception
Returns:
function: A deleter function
"""
def fdel(self):
raise AttributeError("Property '%s' is not deletable by %r"
% (name, self,))
return fdel
class Prop(Unro):
"""A class that stores configuration for a specific property"""
# readonly options
RO_FALSE = 0x0000000
RO_WEAK = 0x0000001
RO_STRONG = 0x0000002
RO_CLASS = 0x0000004
# undead options
UD_FALSE = 0x0000000
UD_CLASS = 0x0000001
UD_INSTANCE = 0x0000002
def __init__(self, value=Void,
readonly=False, # True = RO_STRONG | RO_CLASS
store_default=True,
var_name_prefix='_',
var_name_suffix='',
undead=False): # True = UD_CLASS | UD_INSTANCE
"""Prop constructor that creates property config.
Args:
value (any, optional): Default value for the property.
readonly (bool, optional): Unchangeable property. Mutable
values can still be changed inplace. Defaults to False.
Readonly modes can be the following:
RO_WEAK: Property will be readonly but changeable
through internal variable. Defaults to False.
RO_STRONG: Can not be changed through internal
variable because there will be no internal
variable.
RO_CLASS: Readonly at class level i.e the property
itself will be readonly for the defining class.
True: Equvalent to RO_STRONG | RO_CLASS
False: Not readonly
store_default (bool, optional): Whether to store the
default value of the property in `Props.Defaults`.
var_name_prefix (str, optional): Prefix to add to create
internal variable. Defaults to '_'.
var_name_suffix (str, optional): Suffix to add to create
internal variable. Defaults to ''.
undead (bool, optional): Whether the property should be
undead (non deletable). Defaults to False. Undead modes
are following:
UD_CLASS: undead at class level i.e the class
itself won't be able to delete it.
UD_INSTANCE: undead for instance object of the class.
True: Equvalent to UD_CLASS | UD_INSTANCE
False: not undead i.e deletable.
Raises:
ValueError: When an argument fails validation check.
"""
def check_opt(total, opt):
return (total & opt) != 0
self.value = value # Temporary attribute
if readonly is True:
self.readonly = Prop.RO_STRONG | Prop.RO_CLASS
elif readonly is False:
self.readonly = Prop.RO_FALSE
elif isinstance(readonly, int):
self.readonly = readonly
else:
raise ValueError("Invalid value for parameter 'readonly'. "
"Check class `Prop` for assistance.")
if undead is True:
self.undead = Prop.UD_CLASS | Prop.UD_INSTANCE
elif undead is False:
self.undead = Prop.UD_FALSE
elif isinstance(undead, int):
self.undead = undead
else:
raise ValueError("Invalid value for parameter 'undead'. "
"Check class `Prop` for assistance.")
self.var_name_prefix = var_name_prefix
self.var_name_suffix = var_name_suffix
self.store_default = store_default
if not isinstance(self.var_name_prefix, str) \
or not self.var_name_prefix:
raise ValueError("var_name_prefix needs to be a non empty string")
elif self.var_name_prefix.startswith('__'):
raise ValueError("Leading double underscore is not allowed in "
"var_name_prefix")
elif not self.var_name_prefix.startswith('_'):
raise ValueError("var_name_prefix must start with a single "
"underscore")
if not isinstance(self.var_name_suffix, str):
raise ValueError("var_name_suffix needs to be a string")
elif self.var_name_suffix.endswith('__'):
raise ValueError("Trailing double underscore is not allowed in "
"var_name_suffix")
self.is_readonly = check_opt(self.readonly, Prop.RO_STRONG)
self.is_readonly_weak = check_opt(self.readonly, Prop.RO_WEAK)
self.is_readonly_for_class = check_opt(self.readonly, Prop.RO_CLASS)
self.is_undead_for_instance = check_opt(self.undead, Prop.UD_INSTANCE)
self.is_undead_for_class = check_opt(self.undead, Prop.UD_CLASS)
if self.is_readonly_weak and self.is_readonly:
raise ValueError("RO_WEAK and RO_STRONG can not be True at the "
"same time. It's either weak or strong not both")
class _Props():
"""Store information of class properties"""
def __init__(self):
class Keys(ClassReadonly): pass
class Defaults(ClassReadonly): pass
class Conf(ClassReadonly): pass
class Ivan(ClassReadonly): pass
self._Keys_Internal_Var = Keys()
self._Defaults_Internal_Var = Defaults()
self._Conf_Internal_Var = Conf()
self._Ivan_Internal_Var = Ivan()
self._Keys = Keys
self._Defaults = Defaults
self._Conf = Conf
self._Ivan = Ivan
def __setattr__(self, name, value):
# print("\nsetattr %r, %s" % (self, name,))
# if we keep these names in a single place (somewhere in some
# variable), it would be possible to change it.
ks = ['_Keys', '_Defaults', '_Conf', '_Ivan', '_Keys_Internal_Var',
'_Defaults_Internal_Var', '_Conf_Internal_Var',
'_Ivan_Internal_Var']
if name in ks:
# make singleton
if name in self.__dict__:
raise AttributeError("Attribute '%s' is reserved by %r. "
"It can not be set."
% (name, self.__class__,))
else:
super(_Props, self).__setattr__(name, value)
else:
super(_Props, self).__setattr__(name, value)
def __delattr__(self, name):
# if we keep these names in a single place (somewhere in some
# variable), it would be possible to change it.
ks = ['_Keys', '_Defaults', '_Conf', '_Ivan', '_Keys_Internal_Var',
'_Defaults_Internal_Var', '_Conf_Internal_Var',
'_Ivan_Internal_Var']
if name in ks:
raise AttributeError("Attribute '%s' is reserved by %r. It can "
"not be deleted." % (name, self.__class__,))
else:
super(_Props, self).__delattr__(name)
# property
Keys = property(fget=make_fget('Keys', '_Keys_Internal_Var'),
fset=make_nofset('Keys'),
fdel=make_nofdel('Keys'),
doc='Stores the names of properties accessible by '
'attribute with same name. See details in doc for '
'`Props`.')
Defaults = property(fget=make_fget('Defaults', '_Defaults_Internal_Var'),
fset=make_nofset('Defaults'),
fdel=make_nofdel('Defaults'),
doc='Stores the default values of the properties '
'accessible by attribute with same name. See '
'details in doc for `Props`.')
Conf = property(fget=make_fget('Conf', '_Conf_Internal_Var'),
fset=make_nofset('Conf'),
fdel=make_nofdel('Conf'),
doc='Stores configuration of the properties accessible '
'by attribute with same name. See details in doc for '
'`Props`.')
Ivan = property(fget=make_fget('Ivan', '_Ivan_Internal_Var'),
fset=make_nofset('Ivan'),
fdel=make_nofdel('Ivan'),
doc='Stores the internal variable names of the properties'
' accessible by attribute with same name. See details'
' in doc for `Props`.')
# Convenience aliases
K = Keys
D = Defaults
C = Conf
I = Ivan
class PropMeta(ABCMeta):
"""Metaclass for `PropMixin` that will modify the subclasses to
define properties automatically.
Do note that this is a metaclass, you don't need to inherit it,
rather inherit the `PropMixin` class.
The `Props` attribute of this class will be available through your
class name. For example:
```python
class MyClass(PropMixin):
my_property = Prop('Building A/2')
default_value = MyClass.Props.Defaults.my_property
```
"""
Props = property(fget=make_fget('Props', '_Props_'),
fset=make_nofset('Props'),
fdel=make_nofdel('Props'),
doc="""This attribute contains some other attributes to
provide more information about properties.
Keys
====
Contains the name of the properties accessible as
attributes. For example, an attribute named 'author_name'
can be accessed as: `Props.Keys.author_name`. It will
return the name of the attribute as string: 'author_name'
Defaults
========
Stores the default values of properties.
`Props.Defaults.author_name` will return the default
value of `author_name` attribute.
Conf
====
Stores the configuration of property.
`Props.Conf.author_name` will return a `Prop` object.
Ivan
====
Stores the internal variable name of property.
`Props.Ivan.author_name` will return the name of the
internal variable for `author_name` property as `str`.
""")
def __delattr__(self, name):
# if we keep this name in a single place (somewhere in some
# variable), it would be possible to change it.
if name == '_Props_':
raise AttributeError("'%s' is reserved by %r as an internal "
"variable name. It can not be deleted."
% (name, self.__class__,))
try:
isProp = getattr(self.Props.Conf, name)
# ^returns None or Prop()
# if None, then it's not a property
except:
isProp = None
if isProp:
if isProp.is_undead_for_class:
raise AttributeError("Property '%s' is not deletable by %r"
% (name, self,))
delattr(self.Props._Keys, name)
delattr(self.Props._Conf, name)
if hasattr(self.Props._Defaults, name):
delattr(self.Props._Defaults, name)
# unlike others internal variable is not always available:
if hasattr(self.Props._Ivan, name):
delattr(self.Props._Ivan, name)
super(PropMeta, self).__delattr__(name)
def __setattr__(self, name, value):
# if we keep this name in a single place (somewhere in some
# variable), it would be possible to change it.
if name == '_Props_':
if name in self.__dict__:
raise AttributeError("'%s' is reserved by %r as an internal "
"variable name."
% (name, self.__class__,))
else:
super(PropMeta, self).__setattr__(name, value)
else:
reserved = ['VarConf',]
if name in reserved:
raise AttributeError("Attribute name '%s' is reserved by %r."
% (name, self.__class__,))
if not name.startswith('_'):
try:
prop = getattr(self.Props.Conf, name, None)
except:
prop = None
if isinstance(prop, Prop):
# trying to overwrite a Prop() definition itself.
# should we allow it?
# ...
# !!?
# give option: check whether it should be allowed
# or not
if prop.is_readonly_for_class:
raise AttributeError("Property '%s' is readonly for "
"%r" % (name, self,))
if not isinstance(value, Prop):
val = value
p = self._get_var_conf(name, value)
if p:
# returned a Prop, this one needs to be
# converted to property
value = p
else:
# value is Prop
val = value.value
# now value is OK for final processing
if isinstance(value, Prop):
# print("Creating property '%s' for class '%r'"
# % (name, self))
(This_Prop,
Defaults_Prop,
Keys_Prop,
Ivan_Prop,
Conf_Prop) = self._makePropProperties(name, value, val)
super(PropMeta, self).__setattr__(name, This_Prop)
setattr(self.Props._Conf, name, Conf_Prop)
setattr(self.Props._Keys, name, Keys_Prop)
if Defaults_Prop:
setattr(self.Props._Defaults, name, Defaults_Prop)
# unlike others internal variable is not always
# available:
if Ivan_Prop:
setattr(self.Props._Ivan, name, Ivan_Prop)
else:
super(PropMeta, self).__setattr__(name, value)
else:
super(PropMeta, self).__setattr__(name, value)
def _makePropProperties(self, n, p, val):
"""Return a tuple of all property objects"""
var_name = ''.join([p.var_name_prefix, n, p.var_name_suffix])
nofset = make_nofset(n)
if not p.is_undead_for_instance:
# name nfdel comes from fdel only on name (n)
nfdel = make_fdel(n)
main_property_fdel = make_fdel(n, var_name)
else:
nfdel = make_nofdel(n)
main_property_fdel = nfdel
dfget = make_fget_const(n, val) # used more than once
Conf_Prop = property(fget=make_fget_const(n, p), fset=nofset,
fdel=nfdel)
Keys_Prop = property(fget=make_fget_const(n, n), fset=nofset,
fdel=nfdel)
if p.store_default:
Defaults_Prop = property(fget=dfget, fset=nofset, fdel=nfdel)
else:
Defaults_Prop = None
Ivan_Prop = None
# default value is always readonly ^:
# it does not make sense to change default value later as it
# will have no effect because value will act on its own
# deepcopy version.
# main property configuration
if p.is_readonly:
# constant value, no internal vars
fset = nofset
fget = dfget
fdel = nfdel
elif p.is_readonly_weak:
# value can not be set through property but internal var
# thus value is not constant.
fset = nofset
fget = make_fget(n, var_name, deepcopy(val))
fdel = main_property_fdel
# save the internal var name in Ivan
Ivan_Prop = property(fget=make_fget_const(n, var_name),
fset=nofset, fdel=nfdel)
else:
fset = make_fset(n, var_name)
fget = make_fget(n, var_name, deepcopy(val))
fdel = main_property_fdel
# save the internal var name in Ivan
Ivan_Prop = property(fget=make_fget_const(n, var_name),
fset=nofset, fdel=nfdel)
This_Prop = property(fget=fget, fset=fset, fdel=fdel)
return This_Prop, Defaults_Prop, Keys_Prop, Ivan_Prop, Conf_Prop
def _get_var_conf(self, name, value):
"""Either return Prop object or None"""
# print("\nchecking var_conf for "+name)
try:
var_conf = self.VarConf()
except:
raise TypeError("'VarConf' is a reserved attribute name. It must "
"be a class that inherits and implements "
"`ocd.abc.VarConf`.")
if isinstance(var_conf, abc.VarConf): # must do this check
# because if some other class implementation provide
# get_conf method with name/value arg,
# we do not want to accept unknown entities.
try:
p = var_conf.get_conf(name, value)
except:
raise TypeError("Bad implementation of `VarConf` class. See "
"`ocd.abc.VarConf`")
else:
raise TypeError("'VarConf' is a reserved attribute name. It must "
"be a class that inherits and implements "
"`ocd.abc.VarConf`.")
assert p is None or isinstance(p, Prop), "return value from "\
"'get_conf' in class "\
"'VarConf' inside class "\
"'%r' needs to either "\
"return `None` or a `Prop`"\
" object. See example in "\
"`ocd.abc.VarConf`"\
% (self.__class__,)
return p
# def __init__(cls, name, bases, attrs):
# super(PropMeta, cls).__init__(name, bases, attrs)
def __new__(mcs, class_name, bases, attrs):
rserved_attrs = ['Props', '_Props_']
for K in rserved_attrs:
if K in attrs:
raise AttributeError("'%s' is a reserved attribute for class"
"'%s' defined in '%r'. Please do not "
"redefine it." % (K, class_name, mcs,))
cls = super(PropMeta, mcs).__new__(mcs, class_name, bases, attrs)
cls._Props_ = _Props()
# prop_candidates = {}
non_candidates = ['VarConf']
for k in attrs:
if k.startswith('_') or k in non_candidates:
pass
else:
# print("\n" + k)
setattr(cls, k, attrs[k])
return clsFunctions
def make_fdel(name, var_name=None)-
Make a deleter for
property()'sfdelparamArgs
name:str- property name
var_name:str- internal variable name.
Returns
function- A deleter function
Expand source code
def make_fdel(name, var_name=None): """Make a deleter for `property()`'s `fdel` param Args: name (str): property name var_name (str): internal variable name. Returns: function: A deleter function """ def fdel(self): if var_name: delattr(self, var_name) else: raise AttributeError("Constant readonly property '%s' can not be " "deleted by %r" % (name, self,)) return fdel def make_fget(name, var_name, default=<ocd.types.VoidType object>)-
Return a function compatible with
property()functionfgetparameterArgs
name:str- name of the property
var_name:str- internal variable name
default:any, optional- Default value. Defaults to Void.
Raises
AttributeError- when fails to get the attribute
Returns
function- A getter function
Expand source code
def make_fget(name, var_name, default=Void): """Return a function compatible with `property()` function `fget` parameter Args: name (str): name of the property var_name (str): internal variable name default (any, optional): Default value. Defaults to Void. Raises: AttributeError: when fails to get the attribute Returns: function: A getter function """ def fget(self): v = getattr(self, var_name, default) if v is Void: raise AttributeError("Property '%s' is not set yet for %r" % (name, self,)) return v return fget def make_fget_const(name, v)-
Make a getter for
property()functionfgetparam that returns a constant value.Args
name:str- name of the property
v:any- the constant value of the property
Raises
AttributeError- when the constant value is Void
Returns
function- A getter function
Expand source code
def make_fget_const(name, v): """Make a getter for `property()` function `fget` param that returns a constant value. Args: name (str): name of the property v (any): the constant value of the property Raises: AttributeError: when the constant value is Void Returns: function: A getter function """ def fget(self): if v is Void: raise AttributeError("The value of property '%s' is non-existent " "for %r. It can neither be read nor be " "written." % (name, self,)) return v return fget def make_fset(name, var_name)-
Make a setter for
property()'sfsetparam for property name and internal variable nameArgs
name:str- property name
var_name:str- internal variable name
Returns
function- A setter function
Expand source code
def make_fset(name, var_name): """Make a setter for `property()`'s `fset` param for property name and internal variable name Args: name (str): property name var_name (str): internal variable name Returns: function: A setter function """ def fset(self, value): setattr(self, var_name, value) return fset def make_nofdel(name)-
Make a deleter for
property()'sfdelparam that raisesAttributeErrorArgs
name:str- property name
Raises
AttributeError- always raises exception
Returns
function- A deleter function
Expand source code
def make_nofdel(name): """Make a deleter for `property()`'s `fdel` param that raises `AttributeError` Args: name (str): property name Raises: AttributeError: always raises exception Returns: function: A deleter function """ def fdel(self): raise AttributeError("Property '%s' is not deletable by %r" % (name, self,)) return fdel def make_nofset(name)-
Make a setter for
property()'sfsetparam that raisesAttributeErrorArgs
name:str- property name
Raises
AttributeError- always raises exception
Returns
function- A setter function
Expand source code
def make_nofset(name): """Make a setter for `property()`'s `fset` param that raises `AttributeError` Args: name (str): property name Raises: AttributeError: always raises exception Returns: function: A setter function """ def fset(self, value): raise AttributeError("'%s' is a readonly property for %r" % (name, self,)) return fset
Classes
class Prop (value=<ocd.types.VoidType object>, readonly=False, store_default=True, var_name_prefix='_', var_name_suffix='', undead=False)-
A class that stores configuration for a specific property
Prop constructor that creates property config.
Args
value:any, optional- Default value for the property.
readonly:bool, optional- Unchangeable property. Mutable values can still be changed inplace. Defaults to False. Readonly modes can be the following: RO_WEAK: Property will be readonly but changeable through internal variable. Defaults to False. RO_STRONG: Can not be changed through internal variable because there will be no internal variable. RO_CLASS: Readonly at class level i.e the property itself will be readonly for the defining class. True: Equvalent to RO_STRONG | RO_CLASS False: Not readonly
store_default:bool, optional- Whether to store the
default value of the property in
Props.Defaults. var_name_prefix:str, optional- Prefix to add to create internal variable. Defaults to '_'.
var_name_suffix:str, optional- Suffix to add to create internal variable. Defaults to ''.
undead:bool, optional- Whether the property should be undead (non deletable). Defaults to False. Undead modes are following: UD_CLASS: undead at class level i.e the class itself won't be able to delete it. UD_INSTANCE: undead for instance object of the class. True: Equvalent to UD_CLASS | UD_INSTANCE False: not undead i.e deletable.
Raises
ValueError- When an argument fails validation check.
Expand source code
class Prop(Unro): """A class that stores configuration for a specific property""" # readonly options RO_FALSE = 0x0000000 RO_WEAK = 0x0000001 RO_STRONG = 0x0000002 RO_CLASS = 0x0000004 # undead options UD_FALSE = 0x0000000 UD_CLASS = 0x0000001 UD_INSTANCE = 0x0000002 def __init__(self, value=Void, readonly=False, # True = RO_STRONG | RO_CLASS store_default=True, var_name_prefix='_', var_name_suffix='', undead=False): # True = UD_CLASS | UD_INSTANCE """Prop constructor that creates property config. Args: value (any, optional): Default value for the property. readonly (bool, optional): Unchangeable property. Mutable values can still be changed inplace. Defaults to False. Readonly modes can be the following: RO_WEAK: Property will be readonly but changeable through internal variable. Defaults to False. RO_STRONG: Can not be changed through internal variable because there will be no internal variable. RO_CLASS: Readonly at class level i.e the property itself will be readonly for the defining class. True: Equvalent to RO_STRONG | RO_CLASS False: Not readonly store_default (bool, optional): Whether to store the default value of the property in `Props.Defaults`. var_name_prefix (str, optional): Prefix to add to create internal variable. Defaults to '_'. var_name_suffix (str, optional): Suffix to add to create internal variable. Defaults to ''. undead (bool, optional): Whether the property should be undead (non deletable). Defaults to False. Undead modes are following: UD_CLASS: undead at class level i.e the class itself won't be able to delete it. UD_INSTANCE: undead for instance object of the class. True: Equvalent to UD_CLASS | UD_INSTANCE False: not undead i.e deletable. Raises: ValueError: When an argument fails validation check. """ def check_opt(total, opt): return (total & opt) != 0 self.value = value # Temporary attribute if readonly is True: self.readonly = Prop.RO_STRONG | Prop.RO_CLASS elif readonly is False: self.readonly = Prop.RO_FALSE elif isinstance(readonly, int): self.readonly = readonly else: raise ValueError("Invalid value for parameter 'readonly'. " "Check class `Prop` for assistance.") if undead is True: self.undead = Prop.UD_CLASS | Prop.UD_INSTANCE elif undead is False: self.undead = Prop.UD_FALSE elif isinstance(undead, int): self.undead = undead else: raise ValueError("Invalid value for parameter 'undead'. " "Check class `Prop` for assistance.") self.var_name_prefix = var_name_prefix self.var_name_suffix = var_name_suffix self.store_default = store_default if not isinstance(self.var_name_prefix, str) \ or not self.var_name_prefix: raise ValueError("var_name_prefix needs to be a non empty string") elif self.var_name_prefix.startswith('__'): raise ValueError("Leading double underscore is not allowed in " "var_name_prefix") elif not self.var_name_prefix.startswith('_'): raise ValueError("var_name_prefix must start with a single " "underscore") if not isinstance(self.var_name_suffix, str): raise ValueError("var_name_suffix needs to be a string") elif self.var_name_suffix.endswith('__'): raise ValueError("Trailing double underscore is not allowed in " "var_name_suffix") self.is_readonly = check_opt(self.readonly, Prop.RO_STRONG) self.is_readonly_weak = check_opt(self.readonly, Prop.RO_WEAK) self.is_readonly_for_class = check_opt(self.readonly, Prop.RO_CLASS) self.is_undead_for_instance = check_opt(self.undead, Prop.UD_INSTANCE) self.is_undead_for_class = check_opt(self.undead, Prop.UD_CLASS) if self.is_readonly_weak and self.is_readonly: raise ValueError("RO_WEAK and RO_STRONG can not be True at the " "same time. It's either weak or strong not both")Ancestors
- Unro
- ocd.unro._Base
- ocd.unro._Object
Class variables
var RO_CLASSvar RO_FALSEvar RO_STRONGvar RO_WEAKvar UD_CLASSvar UD_FALSEvar UD_INSTANCE
class PropMeta (class_name, bases, attrs)-
Metaclass for
PropMixinthat will modify the subclasses to define properties automatically.Do note that this is a metaclass, you don't need to inherit it, rather inherit the
PropMixinclass. ThePropsattribute of this class will be available through your class name. For example:class MyClass(PropMixin): my_property = Prop('Building A/2') default_value = MyClass.Props.Defaults.my_propertyExpand source code
class PropMeta(ABCMeta): """Metaclass for `PropMixin` that will modify the subclasses to define properties automatically. Do note that this is a metaclass, you don't need to inherit it, rather inherit the `PropMixin` class. The `Props` attribute of this class will be available through your class name. For example: ```python class MyClass(PropMixin): my_property = Prop('Building A/2') default_value = MyClass.Props.Defaults.my_property ``` """ Props = property(fget=make_fget('Props', '_Props_'), fset=make_nofset('Props'), fdel=make_nofdel('Props'), doc="""This attribute contains some other attributes to provide more information about properties. Keys ==== Contains the name of the properties accessible as attributes. For example, an attribute named 'author_name' can be accessed as: `Props.Keys.author_name`. It will return the name of the attribute as string: 'author_name' Defaults ======== Stores the default values of properties. `Props.Defaults.author_name` will return the default value of `author_name` attribute. Conf ==== Stores the configuration of property. `Props.Conf.author_name` will return a `Prop` object. Ivan ==== Stores the internal variable name of property. `Props.Ivan.author_name` will return the name of the internal variable for `author_name` property as `str`. """) def __delattr__(self, name): # if we keep this name in a single place (somewhere in some # variable), it would be possible to change it. if name == '_Props_': raise AttributeError("'%s' is reserved by %r as an internal " "variable name. It can not be deleted." % (name, self.__class__,)) try: isProp = getattr(self.Props.Conf, name) # ^returns None or Prop() # if None, then it's not a property except: isProp = None if isProp: if isProp.is_undead_for_class: raise AttributeError("Property '%s' is not deletable by %r" % (name, self,)) delattr(self.Props._Keys, name) delattr(self.Props._Conf, name) if hasattr(self.Props._Defaults, name): delattr(self.Props._Defaults, name) # unlike others internal variable is not always available: if hasattr(self.Props._Ivan, name): delattr(self.Props._Ivan, name) super(PropMeta, self).__delattr__(name) def __setattr__(self, name, value): # if we keep this name in a single place (somewhere in some # variable), it would be possible to change it. if name == '_Props_': if name in self.__dict__: raise AttributeError("'%s' is reserved by %r as an internal " "variable name." % (name, self.__class__,)) else: super(PropMeta, self).__setattr__(name, value) else: reserved = ['VarConf',] if name in reserved: raise AttributeError("Attribute name '%s' is reserved by %r." % (name, self.__class__,)) if not name.startswith('_'): try: prop = getattr(self.Props.Conf, name, None) except: prop = None if isinstance(prop, Prop): # trying to overwrite a Prop() definition itself. # should we allow it? # ... # !!? # give option: check whether it should be allowed # or not if prop.is_readonly_for_class: raise AttributeError("Property '%s' is readonly for " "%r" % (name, self,)) if not isinstance(value, Prop): val = value p = self._get_var_conf(name, value) if p: # returned a Prop, this one needs to be # converted to property value = p else: # value is Prop val = value.value # now value is OK for final processing if isinstance(value, Prop): # print("Creating property '%s' for class '%r'" # % (name, self)) (This_Prop, Defaults_Prop, Keys_Prop, Ivan_Prop, Conf_Prop) = self._makePropProperties(name, value, val) super(PropMeta, self).__setattr__(name, This_Prop) setattr(self.Props._Conf, name, Conf_Prop) setattr(self.Props._Keys, name, Keys_Prop) if Defaults_Prop: setattr(self.Props._Defaults, name, Defaults_Prop) # unlike others internal variable is not always # available: if Ivan_Prop: setattr(self.Props._Ivan, name, Ivan_Prop) else: super(PropMeta, self).__setattr__(name, value) else: super(PropMeta, self).__setattr__(name, value) def _makePropProperties(self, n, p, val): """Return a tuple of all property objects""" var_name = ''.join([p.var_name_prefix, n, p.var_name_suffix]) nofset = make_nofset(n) if not p.is_undead_for_instance: # name nfdel comes from fdel only on name (n) nfdel = make_fdel(n) main_property_fdel = make_fdel(n, var_name) else: nfdel = make_nofdel(n) main_property_fdel = nfdel dfget = make_fget_const(n, val) # used more than once Conf_Prop = property(fget=make_fget_const(n, p), fset=nofset, fdel=nfdel) Keys_Prop = property(fget=make_fget_const(n, n), fset=nofset, fdel=nfdel) if p.store_default: Defaults_Prop = property(fget=dfget, fset=nofset, fdel=nfdel) else: Defaults_Prop = None Ivan_Prop = None # default value is always readonly ^: # it does not make sense to change default value later as it # will have no effect because value will act on its own # deepcopy version. # main property configuration if p.is_readonly: # constant value, no internal vars fset = nofset fget = dfget fdel = nfdel elif p.is_readonly_weak: # value can not be set through property but internal var # thus value is not constant. fset = nofset fget = make_fget(n, var_name, deepcopy(val)) fdel = main_property_fdel # save the internal var name in Ivan Ivan_Prop = property(fget=make_fget_const(n, var_name), fset=nofset, fdel=nfdel) else: fset = make_fset(n, var_name) fget = make_fget(n, var_name, deepcopy(val)) fdel = main_property_fdel # save the internal var name in Ivan Ivan_Prop = property(fget=make_fget_const(n, var_name), fset=nofset, fdel=nfdel) This_Prop = property(fget=fget, fset=fset, fdel=fdel) return This_Prop, Defaults_Prop, Keys_Prop, Ivan_Prop, Conf_Prop def _get_var_conf(self, name, value): """Either return Prop object or None""" # print("\nchecking var_conf for "+name) try: var_conf = self.VarConf() except: raise TypeError("'VarConf' is a reserved attribute name. It must " "be a class that inherits and implements " "`ocd.abc.VarConf`.") if isinstance(var_conf, abc.VarConf): # must do this check # because if some other class implementation provide # get_conf method with name/value arg, # we do not want to accept unknown entities. try: p = var_conf.get_conf(name, value) except: raise TypeError("Bad implementation of `VarConf` class. See " "`ocd.abc.VarConf`") else: raise TypeError("'VarConf' is a reserved attribute name. It must " "be a class that inherits and implements " "`ocd.abc.VarConf`.") assert p is None or isinstance(p, Prop), "return value from "\ "'get_conf' in class "\ "'VarConf' inside class "\ "'%r' needs to either "\ "return `None` or a `Prop`"\ " object. See example in "\ "`ocd.abc.VarConf`"\ % (self.__class__,) return p # def __init__(cls, name, bases, attrs): # super(PropMeta, cls).__init__(name, bases, attrs) def __new__(mcs, class_name, bases, attrs): rserved_attrs = ['Props', '_Props_'] for K in rserved_attrs: if K in attrs: raise AttributeError("'%s' is a reserved attribute for class" "'%s' defined in '%r'. Please do not " "redefine it." % (K, class_name, mcs,)) cls = super(PropMeta, mcs).__new__(mcs, class_name, bases, attrs) cls._Props_ = _Props() # prop_candidates = {} non_candidates = ['VarConf'] for k in attrs: if k.startswith('_') or k in non_candidates: pass else: # print("\n" + k) setattr(cls, k, attrs[k]) return clsAncestors
- abc.ABCMeta
- builtins.type
Instance variables
var Props-
This attribute contains some other attributes to provide more information about properties.
Keys
Contains the name of the properties accessible as attributes. For example, an attribute named 'author_name' can be accessed as:
Props.Keys.author_name. It will return the name of the attribute as string: 'author_name'Defaults
Stores the default values of properties.
Props.Defaults.author_namewill return the default value ofauthor_nameattribute.Conf
Stores the configuration of property.
Props.Conf.author_namewill return aPropobject.Ivan
Stores the internal variable name of property.
Props.Ivan.author_namewill return the name of the internal variable forauthor_nameproperty asstr.Expand source code
def fget(self): v = getattr(self, var_name, default) if v is Void: raise AttributeError("Property '%s' is not set yet for %r" % (name, self,)) return v