Modifying classes in this fashion is also possible, though the benefits are not as immediately apparent. Almost certainly, anything which could be done with class decorators could be done using metaclasses, but using metaclasses is sufficiently obscure that there is some attraction to having an easier way to make simple modifications to classes. For Python 2.4, only function/method decorators are being added.
The current method for transforming functions and methods (for instance, declaring them as a class or static method) is awkward and can lead to code that is difficult to understand. Ideally, these transformations should be made at the same point in the code where the declaration itself is made. This PEP introduces new syntax for transformations of a function or method declaration.
Painters prepare surfaces of building and other structures and then apply paint by means of brushes, rollers or sprayers. They work with varnish, enamels, lacquer and other materials. They may also paint interior rooms or cover walls with paper, fabrics, vinyls or other materials (paperhanger). They must be able to mix paints as well as do sandblasting and waterblasting.
In a previous article, we discussed how to use the strategy pattern to dynamically change an object’s behavior at runtime. Classically, polymorphism in object-oriented design is static and achieved through inheritance; however, with the strategy pattern you can accomplish the same goal dynamically. Indeed, this is an excellent way to handle situations when you need an object to exhibit different behavior at different times. However, it’s worth noting that the strategy pattern requires mutation of the object you’re working with. By using the strategy pattern, you are necessarily changing the algorithm that an object uses for a given behavior. In some situations, it may be preferable not to mutate a given object. Or more likely, you won’t even have the option of mutating an object because it may come from a codebase over which you have no control (such as an external library). Such cases are relatively common; however, it’s still possible to enhance an immutable object’s behavior. One effective means to do so is with the decorator pattern.
Aesthetics is the study of art and beauty; it was an important issue for 18th- and 19th-century philosophers such as Kant and Hegel. Classical philosophers like Plato and Aristotle also theorized about art and painting in particular. Plato disregarded painters (as well as sculptors) in his philosophical system; he maintained that painting cannot depict the truth—it is a copy of reality (a shadow of the world of ideas) and is nothing but a craft, similar to shoemaking or iron casting. By the time of Leonardo, painting had become a closer representation of the truth than painting was in Ancient Greece. Leonardo da Vinci, on the contrary, said that "Italian: La Pittura è cosa mentale" ("English: painting is a thing of the mind"). Kant distinguished between Beauty and the Sublime, in terms that clearly gave priority to the former. Although he did not refer to painting in particular, this concept was taken up by painters such as J.M.W. Turner and Caspar David Friedrich.
Painting is an important form in the visual arts, bringing in elements such as drawing, gesture (as in gestural painting), composition, narration (as in narrative art), or abstraction (as in abstract art). Paintings can be naturalistic and representational (as in a still life or landscape painting), photographic, abstract, narrative, symbolistic (as in Symbolist art), emotive (as in Expressionism), or political in nature (as in Artivism).