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 @.
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.

Painters and paperhangers stand for prolonged periods. Their jobs also require a considerable amount of climbing, bending, kneeling, crouching, crawling and reaching with arms raised overhead often on scaffolding, ladders, and working at heights. Painters often work outdoors but seldom in wet, cold or inclement weather. Painters wear masks to reduce exposure to hazardous materials or paint fumes when working in areas with poor ventilation. Much of the work is done alone requiring independent thinking, safety awareness and ability to communicate with the customer. Special equipment is often used; such as equipment for welding, for use while scaffolding, on booms and lifts.

Ink paintings are done with a liquid that contains pigments and/or dyes and is used to color a surface to produce an image, text, or design. Ink is used for drawing with a pen, brush, or quill. Ink can be a complex medium, composed of solvents, pigments, dyes, resins, lubricants, solubilizers, surfactants, particulate matter, fluorescers, and other materials. The components of inks serve many purposes; the ink’s carrier, colorants, and other additives control flow and thickness of the ink and its appearance when dry.
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:
Painters deal practically with pigments,[6] so "blue" for a painter can be any of the blues: phthalocyanine blue, Prussian blue, indigo, Cobalt blue, ultramarine, and so on. Psychological and symbolical meanings of color are not, strictly speaking, means of painting. Colors only add to the potential, derived context of meanings, and because of this, the perception of a painting is highly subjective. The analogy with music is quite clear—sound in music (like a C note) is analogous to "light" in painting, "shades" to dynamics, and "coloration" is to painting as the specific timbre of musical instruments is to music. These elements do not necessarily form a melody (in music) of themselves; rather, they can add different contexts to it.