Metaclass
in a programming language, class whose instances are classes
In object-oriented programming, a metaclass is a class whose syntactic definitions are used for the syntactic definition of the classes themselves. Unlike ordinary classes, which define the behaviors of objects, metaclasses specify the behaviors of classes and their instances. Not all object-oriented programming languages support the concept of metaclasses. For those that do, the extent of control metaclasses have over class behaviors varies. Metaclasses are often implemented by treating classes as first-class citizens, making a metaclass an object that creates and manages these classes. Each programming language adheres to its own metaobject protocol, which are the rules that determine interactions among objects, classes, and metaclasses. Metaclasses are utilized to automate code generation and to enhance framework development.
Python example
In Python, the builtin class type is a metaclass. Consider this simple Python class:
At run time, Car itself is an instance of type. The source code of the Car class, shown above, does not include such details as the size in bytes of Car objects, their binary layout in memory, how they are allocated, that the __init__ method is automatically called each time a Car is created, and so on.
“Metaclass” enters the record as in a programming language, class whose instances are classes. Crown Archives preserves that source wording while asking what Metaclass, programming and language can confirm, complicate or overturn.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Aug 5, 2026. The linked authority identifier is Q1924819. None of the 0 selected statements returned an explicit reference.
A concise general-reference account can conceal disagreements about scope, terminology or the weight assigned to individual sources. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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This entry incorporates text from “Metaclass” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.