As an example, consider a window in a windowing system. To allow scrolling of the window's contents, one may wish to add horizontal or vertical scrollbars to it, as appropriate. Assume windows are represented by instances of the Window interface, and assume this class has no functionality for adding scrollbars. One could create a subclass ScrollingWindow that provides them, or create a ScrollingWindowDecorator that adds this functionality to existing Window objects. At this point, either solution would be fine.
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.
One of the other advantages of the decorator pattern is that wrapped objects can retain the type of the original object. As a result, you can use original and wrapped objects interchangeably, which is a significant advantage when your goal is to write flexible code. In this manner, you can easily extend the behavior of a particular object without modifying the original code.
The container must inject a delegate object to the delegate injection point. The delegate object implements the delegate type and delegates method invocations to remaining uninvoked decorators and eventually to the bean. When the container calls a decorator during business method interception, the decorator may invoke any method of the delegate object.
This decorator works by storing the time just before the function starts running (at the line marked # 1) and just after the function finishes (at # 2). The time the function takes is then the difference between the two (at # 3). We use the time.perf_counter() function, which does a good job of measuring time intervals. Here are some examples of timings:
A painter & decorator is responsible for preparing a surface and applying a range of finishes to it in response to the particular specifications of a job, paying close attention to detail to create a quality end product. The specific role of the painter & decorator is to prepare and decorate a particular surface in accordance with the wishes of the client. This will involve working on a wide variety of surfaces, including metal, wood, plaster and stone, and incorporating numerous materials, such as paint, varnish and wallpaper. The jobs involved depend upon the area that the painter & decorator works in. This can range from the industrial, specially-trained worker supplying skills for a large company, to the part-time, self-employed worker complementing a pension. A lot of the roles of the painter & decorator will come somewhere in between. If working for a larger construction firm, work can include more industrial-scale jobs, such as working as part of a team to prepare and paint the interior of a building or office. This will often involve specialist industrial techniques and larger equipment. If self-employed, this will normally include working independently on smaller jobs such as decorating private houses, schools, shops and other local buildings.
Painters deal practically with pigments, 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.