In general, functions in Python may also have side effects rather than just turning an input into an output. The print() function is a basic example of this: it returns None while having the side effect of outputting something to the console. However, to understand decorators, it is enough to think about functions as something that turns given arguments into a value.
Just take a look at the code again. In the if/else clause we are returning greet and welcome, not greet() and welcome(). Why is that? It’s because when you put a pair of parentheses after it, the function gets executed; whereas if you don’t put parenthesis after it, then it can be passed around and can be assigned to other variables without executing it. Did you get it? Let me explain it in a little bit more detail. When we write a = hi(), hi() gets executed and because the name is yasoob by default, the function greet is returned. If we change the statement to a = hi(name = "ali") then the welcome function will be returned. We can also do print hi()() which outputs now you are in the greet() function.
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.
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The .__init__() method must store a reference to the function and can do any other necessary initialization. The .__call__() method will be called instead of the decorated function. It does essentially the same thing as the wrapper() function in our earlier examples. Note that you need to use the functools.update_wrapper() function instead of @functools.wraps.
Tempera, also known as egg tempera, is a permanent, fast-drying painting medium consisting of colored pigment mixed with a water-soluble binder medium (usually a glutinous material such as egg yolk or some other size). Tempera also refers to the paintings done in this medium. Tempera paintings are very long lasting, and examples from the first centuries CE still exist. Egg tempera was a primary method of painting until after 1500 when it was superseded by the invention of oil painting. A paint commonly called tempera (though it is not) consisting of pigment and glue size is commonly used and referred to by some manufacturers in America as poster paint.
Peter Heller is the best-selling author of The Dog Stars. He holds an MFA from the Iowa Writers’ Workshop in both fiction and poetry. An award-winning adventure writer and a longtime contributor to NPR, Heller is a contributing editor at Outside magazine, Men’s Journal, and National Geographic Adventure, and a regular contributor to Bloomberg Businessweek. He is also the author of several nonfiction books, including Kook, The Whale Warriors, and Hell or High Water: Surviving Tibet’s Tsangpo River. He lives in Denver, Colorado.
Rhythm is important in painting as it is in music. If one defines rhythm as "a pause incorporated into a sequence", then there can be rhythm in paintings. These pauses allow creative force to intervene and add new creations—form, melody, coloration. The distribution of form, or any kind of information is of crucial importance in the given work of art, and it directly affects the aesthetic value of that work. This is because the aesthetical value is functionality dependent, i.e. the freedom (of movement) of perception is perceived as beauty. Free flow of energy, in art as well as in other forms of "techne", directly contributes to the aesthetical value.