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This example is in Smalltalk, of a typical accessor method to return the value of a variable using lazy initialization. height ^ height ifNil: [ height := 2.0 ] . The 'non-lazy' alternative is to use an initialization method that is run when the object is created and then use a simpler accessor method to fetch the value.
Lazy loading (also known as asynchronous loading) is a technique used in computer programming, especially web design and web development, to defer initialization of an object until it is needed. It can contribute to efficiency in the program's operation if properly and appropriately used.
In Python 3.x the range() function [28] returns a generator which computes elements of the list on demand. Elements are only generated when they are needed (e.g., when print(r[3]) is evaluated in the following example), so this is an example of lazy or deferred evaluation: >>>
Python functions decorated with Dask delayed adopt a lazy evaluation strategy by deferring execution and generating a task graph with the function and its arguments. The Python function will only execute when .compute is invoked. Dask delayed can be used as a function dask.delayed or as a decorator @dask.delayed.
A singleton implementation may use lazy initialization in which the instance is created when the static method is first invoked. In multithreaded programs, this can cause race conditions that result in the creation of multiple instances. The following Java 5+ example [6] is a thread-safe implementation, using lazy initialization with double ...
The observer design pattern is a behavioural pattern listed among the 23 well-known "Gang of Four" design patterns that address recurring design challenges in order to design flexible and reusable object-oriented software, yielding objects that are easier to implement, change, test and reuse.
Lazy evaluation Typing Abstract data types Algebraic data types Data is immutable Type classes Garbage collection First appeared Common Lisp: No [1] Simulated with thunks [2] Dynamic [3] Yes [4] Extension [5] No [6]? Yes: 1984 Scheme: No [7] Yes [8] Dynamic [7] Yes [9] Simulated with thunks [10] No [11] No: Yes: 1975 Racket: No: Default in Lazy ...
However, it is not always idiomatic in such languages, and is specifically discouraged in Python (in favor of context managers and finalizers from the weakref package). [ citation needed ] However, object lifetimes are not necessarily bound to any scope, and objects may be destroyed non-deterministically or not at all.