Ng|dZddlmZddlZddlmZmZmZmZm Z eddZ Gdd ee Z dS) z:Stand-alone utility functions independent of OXMSG domain.) annotationsN)AnyCallableGenericTypeVarcast_TT) covariantc,eZdZdZddZddd ZddZdS) lazypropertya$Decorator like @property, but evaluated only on first access. Like @property, this can only be used to decorate methods having only a `self` parameter, and is accessed like an attribute on an instance, i.e. trailing parentheses are not used. Unlike @property, the decorated method is only evaluated on first access; the resulting value is cached and that same value returned on second and later access without re-evaluation of the method. Like @property, this class produces a *data descriptor* object, which is stored in the __dict__ of the *class* under the name of the decorated method ('fget' nominally). The cached value is stored in the __dict__ of the *instance* under that same name. Because it is a data descriptor (as opposed to a *non-data descriptor*), its `__get__()` method is executed on each access of the decorated attribute; the __dict__ item of the same name is "shadowed" by the descriptor. While this may represent a performance improvement over a property, its greater benefit may be its other characteristics. One common use is to construct collaborator objects, removing that "real work" from the constructor, while still only executing once. It also de-couples client code from any sequencing considerations; if it's accessed from more than one location, it's assured it will be ready whenever needed. Loosely based on: https://stackoverflow.com/a/6849299/1902513. A lazyproperty is read-only. There is no counterpart to the optional "setter" (or deleter) behavior of an @property. This is critically important to maintaining its immutability and idempotence guarantees. Attempting to assign to a lazyproperty raises AttributeError unconditionally. The parameter names in the methods below correspond to this usage example:: class Obj(object) @lazyproperty def fget(self): return 'some result' obj = Obj() Not suitable for wrapping a function (as opposed to a method) because it is not callable. fgetCallable[..., _T]returnNonecV||_|j|_tj||dS)aY*fget* is the decorated method (a "getter" function). A lazyproperty is read-only, so there is only an *fget* function (a regular @property can also have an fset and fdel function). This name was chosen for consistency with Python's `property` class which uses this name for the corresponding parameter. N)_fget__name___name functoolsupdate_wrapper)selfr s F/var/www/html/ai-engine/env/lib/python3.11/site-packages/oxmsg/util.py__init__zlazyproperty.__init__6s- ]  t,,,,,Nobjrtyper c||S|j|j}|$||}||j|j<t t |S)aCalled on each access of 'fget' attribute on class or instance. *self* is this instance of a lazyproperty descriptor "wrapping" the property method it decorates (`fget`, nominally). *obj* is the "host" object instance when the attribute is accessed from an object instance, e.g. `obj = Obj(); obj.fget`. *obj* is None when accessed on the class, e.g. `Obj.fget`. *type* is the class hosting the decorated getter method (`fget`) on both class and instance attribute access. )__dict__getrrrr )rrrvalues r__get__zlazyproperty.__get__EsY ;K   ,, =JJsOOE',CL $Brr c td)aRaises unconditionally, to preserve read-only behavior. This decorator is intended to implement immutable (and idempotent) object attributes. For that reason, assignment to this property must be explicitly prevented. If this __set__ method was not present, this descriptor would become a *non-data descriptor*. That would be nice because the cached value would be accessed directly once set (__dict__ attrs have precedence over non-data descriptors on instance attribute lookup). The problem is, there would be nothing to stop assignment to the cached value, which would overwrite the result of `fget()` and break both the immutability and idempotence guarantees of this decorator. The performance with this __set__() method in place was roughly 0.4 usec per access when measured on a 2.8GHz development machine; so quite snappy and probably not a rich target for optimization efforts. zcan't set attribute)AttributeError)rrr s r__set__zlazyproperty.__set__bs&2333r)r rrr)N)rrrrrr )rrr rrr)r __module__ __qualname____doc__rr!r$rrr r s`((T - - - -:444444rr ) r' __future__rrtypingrrrrrr r r(rrr+s@@""""""88888888888888 WTT"""j4j4j4j4j472;j4j4j4j4j4r