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SQLAlchemy offers tools for database schema generation, querying, and object-relational mapping. Key features include: A comprehensive embedded domain-specific language for SQL in Python called "SQLAlchemy Core" that provides means to construct and execute SQL queries. A powerful ORM that allows the mapping of Python classes to database tables.
In class-based, object-oriented programming, a constructor (abbreviation: ctor) is a special type of function called to create an object. It prepares the new object for use, often accepting arguments that the constructor uses to set required member variables.
In object-oriented programming, a factory is an object for creating other objects; formally, it is a function or method that returns objects of a varying prototype or class [1] from some method call, which is assumed to be new. [a] More broadly, a subroutine that returns a new object may be referred to as a factory, as in factory method or ...
It should be possible to define a new operation for (some) classes of an object structure without changing the classes. When new operations are needed frequently and the object structure consists of many unrelated classes, it's inflexible to add new subclasses each time a new operation is required because "[..] distributing all these operations across the various node classes leads to a system ...
It is used when the types of objects to create is determined by a prototypical instance, which is cloned to produce new objects. This pattern is used to avoid subclasses of an object creator in the client application, like the factory method pattern does, and to avoid the inherent cost of creating a new object in the standard way (e.g., using ...
The detailed semantics of "the" ternary operator as well as its syntax differs significantly from language to language. A top level distinction from one language to another is whether the expressions permit side effects (as in most procedural languages) and whether the language provides short-circuit evaluation semantics, whereby only the selected expression is evaluated (most standard ...
In Python, if a name is intended to be "private", it is prefixed by one or two underscores. Private variables are enforced in Python only by convention. Names can also be suffixed with an underscore to prevent conflict with Python keywords. Prefixing with double underscores changes behaviour in classes with regard to name mangling.
The object pool design pattern is used in several places in the standard classes of the .NET Framework. One example is the .NET Framework Data Provider for SQL Server. As SQL Server database connections can be slow to create, a pool of connections is maintained. Closing a connection does not actually relinquish the link to SQL Server.