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...object.__init_subclass__. But given that it is a common mistake to forget to call super(), it would happen too often that suddenly descriptors are not initialized. Key Benefits Easier inheritance of definition time behaviour Understanding Python's metaclasses requires a deep understanding of the type system and the class construction process. This is legitimately seen as challenging, due to the need to keep multiple moving parts (the code, the metaclass hint, the actual metaclass, the class o...
...definitions only allow simple function names to be used, even though functions are assignable first class objects. This PEP proposes adding support for assigning a function to a class or instance attribute directly in the function definition's header by using the dot notation to separate the object from the function's name. Although a similar feature, this PEP does not address general assignment to anything that supports assignment, such as dict keys and list indexes. Rationale Currently if a ...
...objection to this option is that there is no obvious object where the dispatch dict can be stored. It can't be stored on the code object, which is supposed to be immutable; it can't be stored on the function object, since many function objects may be created for the same function (e.g. for nested functions). In practice, I'm sure that something can be found; it could be stored in a section of the code object that's not considered when comparing two code objects or when pickling or marshalling ...
...object is never callable. So what do Don and Jim do in order to use Don's hook? Write an extension that defines at least two new Python object types. The first would be the type for ``class-like'' objects usable as a base class, to trigger Don's hook. This type must be made callable. That's why we need a second type. Whether an object is callable depends on its type. So whether a type object is callable depends on its type, which is a meta-type. (In core Python there is only one...
...object returns a bytes object. Slicing a bytearray object returns a bytearray object. Slice assignment to a bytearray object accepts anything that implements the PEP 3118 buffer API, or an iterable of integers in range(256). Indexing Indexing bytes and bytearray returns small ints (like the bytes type in 3.0a1, and like lists or array.array('B')). Assignment to an item of a bytearray object accepts an int in range(256). (To assign from a bytes sequence, use a slice assignment.) Str() and R...
...Objects/codeobject.c; contains definition of PyCodeObject. symtable.h Header for Python/symtable.c . struct symtable and PySTEntryObject are defined here. pyarena.h Header file for the corresponding Python/pyarena.c . opcode.h Master list of bytecode; if this file is modified you must modify several other files accordingly (see "Introducing New Bytecode") Objects/ codeobject.c Contains PyCodeObject-related code (originally in Python/compile.c). Lib/ opcode.py One of the files...
...objects: regular objects (like lists, ints, functions) and meta-objects. Types and classes are meta-objects. Meta-objects are also regular objects, but we're mostly interested in them because they are referenced by the __class__ attribute of regular objects (or by the __bases__ attribute of other meta-objects). The class introspection API consists of the following elements: the __class__ and __dict__ attributes on regular objects; the __bases__ and __dict__ attributes on meta-objects; preceden...
...object): pass @overload def foo(bar:object, baz:int): pass In contrast, the following pair of implementations can never be ambiguous, because one signature always implies the other; the int/int signature is more specific than the object/object signature: def foo(bar:object, baz:object): pass @overload def foo(bar:int, baz:int): pass A signature S1 implies another signature S2, if whenever S1 would apply, S2 would also. A signature S1 is "more specific" than another signatur...
...definition in the function or class body. The name of the object being declared is the first thing stated after the keyword. Other important information is also given the honour of preceding the implementation details: decorators (which can greatly affect the behaviour of the created object, and were placed ahead of even the keyword and name as a matter of practicality more so than aesthetics) the docstring (on the first line immediately following the header line) parameters, default values and...
...objects should be controlled through the Python memory management, usage of "static" type objects is discouraged, unless the type object itself has no memory-managed state. To simplify definition of heap types, a new method: PyTypeObject* PyType_Copy(PyTypeObject*); is added. Example xxmodule.c would be changed to remove the initxx function, and add the following code instead: struct xxstate{ PyObject *ErrorObject; PyObject *Xxo_Type; }; #define xxstate(o) ((struct xxstate*)PyModule_Ge...
...definition time. Instead, they are preserved in __annotations__ in string form. This change is being introduced gradually, starting with a __future__ import in Python 3.7. Rationale and Goals PEP 3107 added support for arbitrary annotations on parts of a function definition. Just like default values, annotations are evaluated at function definition time. This creates a number of issues for the type hinting use case: forward references: when a type hint contains names that have not been defi...
...definition file. Like YACC, YAPPS supports custom code before and after the grammar definition. YAPPS parsers integrate with the scanner through a Scanner object, which is passed to the parser as a constructor argument. Even though YAPPS supports definition of tokens in the grammar, we have not used this capability in XPath, since we have provided my own scanner class. The YAPPS parser will only require a token() method from the scanner object, which must return a four-tuple (start, e...
...Objections Transition Plan Approval Implementation References Copyright Abstract The iterator protocol in Python 2.x consists of two methods: __iter__() called on an iterable object to yield an iterator, and next() called on an iterator object to yield the next item in the sequence. Using a for loop to iterate over an iterable object implicitly calls both of these methods. This PEP proposes that the next method be renamed to __next__, consistent with all the other protocols in Python in whi...
...objects Sometimes you want to talk about class objects, in particular class objects that inherit from a given class. This can be spelled as Type[C] where C is a class. To clarify: while C (when used as an annotation) refers to instances of class C, Type[C] refers to subclasses of C. (This is a similar distinction as between object and type.) For example, suppose we have the following classes: class User: ... # Abstract base for User classes class BasicUser(User): ... class ProUser(User): .....
...object with a write() method (i.e. a file-like object). Thus these two statements are equivalent: print 'hello world' print >> sys.stdout, 'hello world' As are these two statements: print print >> sys.stdout These two statements are syntax errors: print , print >> sys.stdout, Justification 'print' is a Python keyword and introduces the print statement as described in section 6.6 of the language reference manual [1]. The print statement has a number of features: it aut...
...definition of namespace that would make this work is: class namespace(object): def __init__(self, name, args, kwargs): self.__dict__.update(kwargs) Given this definition, at the end of the make-statements above, roletypes and format would be namespace instances. Example: GUI objects In GUI toolkits, objects like frames and panels are often associated with attributes and functions. With the make-statement, code that looks something like: root = Tkinter.Tk() frame = Tkinter.Frame...
...Object *PyCMethod( PyObject *self, // object the method was called on PyTypeObject *defining_class, // defining class PyObject *const *args, // C array of arguments Py_ssize_t nargs, // length of "args" PyObject *kwnames) // NULL, or dict of keyword arguments Once you have the defining class, call PyType_GetModuleState to get the state of its associated module. For example: static PyObject * example_method(PyObject *self, ...
...Object_GC_Init() after the initialization of the object's container attributes is complete. pyexpat adds definitions of PyModule_AddStringConstant and PyModule_AddObject if the Python version is less than 2.0, which provides compatibility with PyXML on Python 1.5.2. If the platform has a bogus definition for LONG_BIT (the number of bits in a long), an error will be reported at compile time. Fix bugs in _PyTuple_Resize() which caused hard-to-interpret garbage collection cr...
...object is an instance of functools.partial, construct a new Signature from its partial.func attribute, and account for already bound partial.args and partial.kwargs If the object is a class or metaclass: If the object's type has a __call__ method defined in its MRO, return a Signature for it If the object has a __new__ method defined in its MRO, return a Signature object for it If the object has a __init__ method defined in its MRO, return a Signature object for it Return signature(object.__ca...
...definition of subtyping above, this places Any partially at the top (it has all values) and bottom (it has all methods) of the type hierarchy. Contrast this to object -- it is not consistent with most types (e.g. you can't use an object() instance where an int is expected). IOW both Any and object mean "any type is allowed" when used to annotate an argument, but only Any can be passed no matter what type is expected (in essence, Any declares a fallback to dynamic typing and shuts up complaints f...