This code works for our purposes but it’s not exactly dynamic. If we wanted our initial simpleMsg object to sometimes act excited and sometimes quizzical, we could only do so by instantiating entirely new objects from the relevant subclass. Moreover, the ExcitedAndQuizzicalMessage is really just a combination of ExcitedMessage and QuizzicalMessage and probably shouldn’t have its own class. To fix these problems, let’s now return to the decorator pattern and see how it might help us.
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.
Here we ensure that the key student_id is part of the request. Although this validation works, it really does not belong in the function itself. Plus, perhaps there are other routes that use the exact same validation. So, let’s keep it DRY and abstract out any unnecessary logic with a decorator. The following @validate_json decorator will do the job:
To calculate the tenth Fibonacci number, you should really only need to calculate the preceding Fibonacci numbers, but this implementation somehow needs a whopping 177 calculations. It gets worse quickly: 21891 calculations are needed for fibonacci(20) and almost 2.7 million calculations for the 30th number. This is because the code keeps recalculating Fibonacci numbers that are already known.
Where The Dog Stars established Heller as a writer with a consistent, wickedly humorous voice, a formidable scene setter, and writer with philosophical underpinnings, this second novel shows those strengths fraying a bit. He’s adopting a voice here that isn’t always his own; he toys with the sentence structures of Hemingway and Raymond Carver, and the effect is a bit clumsy. However in the book’s second half he returns to vestiges of his first novel’s voice, and this is where his story becomes compelling.

Style is used in two senses: It can refer to the distinctive visual elements, techniques and methods that typify an individual artist's work. It can also refer to the movement or school that an artist is associated with. This can stem from an actual group that the artist was consciously involved with or it can be a category in which art historians have placed the painter. The word 'style' in the latter sense has fallen out of favor in academic discussions about contemporary painting, though it continues to be used in popular contexts. Such movements or classifications include the following:
Watercolor is a painting method in which the paints are made of pigments suspended in a water-soluble vehicle. The traditional and most common support for watercolor paintings is paper; other supports include papyrus, bark papers, plastics, vellum or leather, fabric, wood and canvas. In East Asia, watercolor painting with inks is referred to as brush painting or scroll painting. In Chinese, Korean, and Japanese painting it has been the dominant medium, often in monochrome black or browns. India, Ethiopia and other countries also have long traditions. Finger-painting with watercolor paints originated in China. Watercolor pencils (water-soluble color pencils) may be used either wet or dry.

Enforcement of this Act by the Painter-Stainers Company was sought up until the early 19th century, with master painters gathering irregularly to decide the fees that a journeyman could charge, and also instigating an early version of a job centre in 1769, advertising in the London newspapers a "house of call" system to advertise for journeymen and also for journeymen to advertise for work. The guild's power in setting the fee a journeyman could charge was eventually overturned by law in 1827, and the period after this saw the guild's power diminish, along with that of the other guilds; the guilds were superseded by trade unions, with the Operative United Painters' Union forming sometime around 1831.[2]


Surrealism is a cultural movement that began in the early 1920s, and is best known for the visual artworks and writings of the group members. Surrealist artworks feature the element of surprise, unexpected juxtapositions and non sequitur; however, many Surrealist artists and writers regard their work as an expression of the philosophical movement first and foremost, with the works being an artifact. Leader André Breton was explicit in his assertion that Surrealism was above all a revolutionary movement.

Did you get it? We just applied the previously learned principles. This is exactly what the decorators do in Python! They wrap a function and modify its behaviour in one way or the another. Now you might be wondering that we did not use the @ anywhere in our code? That is just a short way of making up a decorated function. Here is how we could have run the previous code sample using @.

The invention of photography had a major impact on painting. In the decades after the first photograph was produced in 1829, photographic processes improved and became more widely practiced, depriving painting of much of its historic purpose to provide an accurate record of the observable world. A series of art movements in the late 19th and early 20th centuries—notably Impressionism, Post-Impressionism, Fauvism, Expressionism, Cubism, and Dadaism—challenged the Renaissance view of the world. Eastern and African painting, however, continued a long history of stylization and did not undergo an equivalent transformation at the same time.[citation needed]
×