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In computer programming, initialization or initialisation is the assignment of an initial value for a data object or variable. The manner in which initialization is performed depends on the programming language , as well as the type, storage class, etc., of an object to be initialized.
do end: f do ensure tag: expression end: f do check tag: expression end end: class X invariant tag: expression end: from instructions invariant tag: expression until expr loop instructions variant tag: expression end: Python — PHP Perl Raku PRE {condition } POST {condition } Ruby — Windows PowerShell OCaml F# COBOL
Python supports most object oriented programming (OOP) techniques. It allows polymorphism, not only within a class hierarchy but also by duck typing. Any object can be used for any type, and it will work so long as it has the proper methods and attributes. And everything in Python is an object, including classes, functions, numbers and modules.
In Ruby, all classes are open. In Python, classes can be created at runtime, and all can be modified afterward. [43] Objective-C categories permit the programmer to add methods to an existing class without the need to recompile that class or even have access to its source code.
In Objective-C, the constructor method is split across two methods, "alloc" and "init" with the alloc method setting aside (allocating) memory for an instance of the class, and the init method handling the bulk of initializing the instance. A call to the method "new" invokes both the alloc and the init methods, for the class instance.
Python does not support tail call optimization or first-class continuations, and, according to Van Rossum, it never will. [99] [100] However, better support for coroutine-like functionality is provided by extending Python's generators. [101] Before 2.5, generators were lazy iterators; data was passed unidirectionally out of the generator. From ...
A class diagram exemplifying the singleton pattern.. In object-oriented programming, the singleton pattern is a software design pattern that restricts the instantiation of a class to a singular instance.
If a class does not allow calling code to access internal object data and permits access through methods only, this is also a form of information hiding. Some languages (Java, for example) let classes enforce access restrictions explicitly, for example, denoting internal data with the private keyword and designating methods intended for use by ...