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:
There have been a number of objections raised to this location -- the primary one is that it's the first real Python case where a line of code has an effect on a following line. The syntax available in 2.4a3 requires one decorator per line (in a2, multiple decorators could be specified on the same line), and the final decision for 2.4 final stayed one decorator per line.
Now we have our logit decorator in production, but when some parts of our application are considered critical, failure might be something that needs more immediate attention. Let’s say sometimes you want to just log to a file. Other times you want an email sent, so the problem is brought to your attention, and still keep a log for your own records. This is a case for using inheritence, but so far we’ve only seen functions being used to build decorators.
In England, little is known of the trade and its structures before the late 13th century, at which paint guilds began to form, amongst them the Painters Company and the Stainers Company. These two guilds eventually merged with the consent of the Lord Mayor of the City of London in 1502, forming the Worshipful Company of Painter-Stainers. The guild standardised the craft and acted as a protector of the trade secrets. In 1599, the guild asked Parliament for protection, which was eventually granted in a bill of 1606, which granted the trade protection from outside competition such as plasterers.[2]
Enamels are made by painting a substrate, typically metal, with powdered glass; minerals called color oxides provide coloration. After firing at a temperature of 750–850 degrees Celsius (1380–1560 degrees Fahrenheit), the result is a fused lamination of glass and metal. Unlike most painted techniques, the surface can be handled and wetted Enamels have traditionally been used for decoration of precious objects,[22] but have also been used for other purposes. Limoges enamel was the leading centre of Renaissance enamel painting, with small religious and mythological scenes in decorated surrounds, on plaques or objects such as salts or caskets. In the 18th century, enamel painting enjoyed a vogue in Europe, especially as a medium for portrait miniatures.[23] In the late 20th century, the technique of porcelain enamel on metal has been used as a durable medium for outdoor murals.[24]
As with many construction jobs, those who successfully complete apprenticeships best-position themselves for successful painting careers. For painters, apprenticeships can last up to four years. Apprentices must have a high school diploma or its equivalent before they are eligible to complete the requisite 144 hours of technical instruction and 2,000 hours of paid, on-the-job training. Common lessons include aesthetics, such as how to adequately match colors, as well as using and caring for painting tools and equipment, safety practices, application techniques and wood finishing. Prospective painters may also choose to attend two-year technical schools that offer courses linked to union and contractor organization apprenticeships. Credits gained from apprenticeships typically count toward an associate degree.
Gouache is a water-based paint consisting of pigment and other materials designed to be used in an opaque painting method. Gouache differs from watercolor in that the particles are larger, the ratio of pigment to water is much higher, and an additional, inert, white pigment such as chalk is also present. This makes gouache heavier and more opaque, with greater reflective qualities. Like all watermedia, it is diluted with water.[21]
Modern artists have extended the practice of painting considerably to include, as one example, collage, which began with Cubism and is not painting in the strict sense. Some modern painters incorporate different materials such as sand, cement, straw or wood for their texture. Examples of this are the works of Jean Dubuffet and Anselm Kiefer. There is a growing community of artists who use computers to "paint" color onto a digital "canvas" using programs such as Adobe Photoshop, Corel Painter, and many others. These images can be printed onto traditional canvas if required.