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In Python, functions are first-class objects, just like strings, numbers, lists etc. This feature eliminates the need to write a function object in many cases. Any object with a __call__() method can be called using function-call syntax. An example is this accumulator class (based on Paul Graham's study on programming language syntax and ...
Numba is used from Python, as a tool (enabled by adding a decorator to relevant Python code), a JIT compiler that translates a subset of Python and NumPy code into fast machine code. Pythran compiles a subset of Python 3 to C++ . [165] RPython can be compiled to C, and is used to build the PyPy interpreter of Python.
Python allows the creation of class methods and static methods via the use of the @classmethod and @staticmethod decorators. The first argument to a class method is the class object instead of the self-reference to the instance. A static method has no special first argument. Neither the instance, nor the class object is passed to a static method.
In some languages, for example C++, Java, and Raku this or self is a keyword, and the variable automatically exists in instance methods. In others, for example, Python, Rust, and Perl 5, the first parameter of an instance method is such a reference. It needs to be specified explicitly.
An example would be a static method to sum the values of all the variables of every instance of a class. For example, if there were a Product class it might have a static method to compute the average price of all products. A static method can be invoked even if no instances of the class exist yet.
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 ...
A new instance is created by calling the class as if it were a function, which calls the __new__ and __init__ methods. If a constructor method is not defined in the class, the next one found in the class's Method Resolution Order will be called. [14] In the typical case, only the __init__ method need be defined. (The most common exception is ...
Also, another common example is that a person object created from a child class cannot become an object of parent class because a child class and a parent class inherit a person class but class-based languages mostly do not allow to change the kind of class of the object at runtime. For class-based languages, this restriction is essential in ...