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...type(s) and C output type(s). Default converters must have quoted names, custom converters must have regular names. A Python type is given by its name. If a function accepts multiple Python types, the set is written in list form. Since the default converters may have multiple implicit return values, the C output type(s) are written according to the following convention: The main return value must be named res. This is a placeholder for the actual variable name given later in the DSL. Additiona...
...Type Definition Syntax Acceptable type hints Using None Type aliases Callable Generics User-defined generic types Scoping rules for type variables Instantiating generic classes and type erasure Arbitrary generic types as base classes Abstract generic types Type variables with an upper bound Covariance and contravariance The numeric tower Forward references Union types Support for singleton types in unions The Any type The NoReturn type The type of class objects Annotating instance and class meth...
...definition order is important. Specification Part 1: all classes have a __definition_order__ attribute __definition_order__ is a tuple of identifiers (or None) __definition_order__ is always set: during execution of the class body, the insertion order of names into the class definition namespace is stored in a tuple if __definition_order__ is defined in the class body then it must be a tuple of identifiers or None; any other value will result in TypeError classes that do not have a class defi...
...type objects get created dynamically. To allow an easy creation of types (in particular, to be able to fill out function pointers easily), the following structures and functions are available: typedef struct{ int slot; /* slot id, see below */ void *pfunc; /* function pointer */ } PyType_Slot; typedef struct{ const char* name; int basicsize; int itemsize; unsigned int flags; PyType_Slot *slots; /* terminated by slot==0. */ } PyType_Spec; PyObject* PyType_FromSpec(PyType_Spec*...
...type and you're in business. There's a new built-in name, "dict", for the type of dictionaries. (In version 2.2b1 and before, this was called "dictionary"; while in general I don't like abbreviations, "dictionary" was just too long to type, and we've been saying "dict" for years.) This is really just sugar, since there are already two other ways to name this type: type({}) and (after importing the types module) types.DictType (and a third, types.DictionaryType). But now that types p...
...type checker is the subtype relationship. It arises from the question: If first_var has type first_type, and second_var has type second_type, is it safe to assign first_var = second_var? A strong criterion for when it should be safe is: every value from second_type is also in the set of values of first_type; and every function from first_type is also in the set of functions of second_type. The relation defined thus is called a subtype relation. By this definition: Every type is a subtype of i...
...type.__new__ is slightly changed, raising fears of backwards compatibility. It should be assured by tests that common use cases behave as desired. The following class definitions (except the one defining the metaclass) continue to fail with a TypeError as superfluous class arguments are passed: class MyMeta(type): pass class MyClass(metaclass=MyMeta, otherarg=1): pass MyMeta("MyClass", (), otherargs=1) import types types.new_class("MyClass", (), dict(metaclass=MyMeta, otherarg=1)) ty...
...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 meta-type, the type ``type'' (types.TypeType), which is the type of all type objects, even itself.) A new meta-type must be defined that makes the type of the class-like objects callable. (Normally, a third type would also be needed, the new ``instance'' type, ...
...type definitions: T = TypeVar('T', bound='<type>') UserId = NewType('UserId', '<type>') Employee = NamedTuple('Employee', [('name', '<type>'), ('id', '<type>')]) aliases: Alias = Optional['<type>'] AnotherAlias = Union['<type>', '<type>'] YetAnotherAlias = '<type>' casting: cast('<type>', value) base classes: class C(Tuple['<type>', '<type>']): ... Depending on the specific case, some of the cases listed above might b...
...types and its dynamic typing. For example, a Python programmer wastes no time declaring the types of arguments or variables, and Python's powerful polymorphic list and dictionary types, for which rich syntactic support is built straight into the language, find a use in almost every Python program. Because of the run-time typing, Python's run time must work harder than Java's. For example, when evaluating the expression a+b, it must first inspect the objects a and b to find out their type,...
...types (except in a limited form for arithmetic operators, where "right-hand" (__r*__) methods can be used to do two-argument dispatch. In addition, it is currently a common anti-pattern for Python code to inspect the types of received arguments, in order to decide what to do with the objects. For example, code may wish to accept either an object of some type, or a sequence of objects of that type. Currently, the "obvious way" to do this is by type inspection, but this is brittle and closed to ...
...type (usually string or tuple). With the new scheme, the type is a class and the value is a class instance. For example, the following code will break: try: raise Exception() except: print "Sorry:", sys.exc_type + ":", sys.exc_value because it tries to concatenate the exception type (a class object) with a string. A fix (also for the previous example) would be to write try: raise Exception() except: etype = sys.exc_type # Save it; try-excep...
...type information at runtime, and deferring all check to static type checkers only: typedef struct { PyObject_HEAD /* ... your code ... */ } SimpleGeneric; static PyObject * simple_class_getitem(PyObject *type, PyObject *item) { Py_INCREF(type); return type; } static PyMethodDef simple_generic_methods[] = { {"__class_getitem__", simple_class_getitem, METH_O|METH_CLASS, NULL}, /* ... other methods ... */ }; PyTypeObject SimpleGeneric_Type = { PyVarObject_HEAD_INIT(N...
...type of a concrete type. A concrete type X is a subtype of protocol P if and only if X implements all protocol members of P with compatible types. In other words, subtyping with respect to a protocol is always structural. A protocol P1 is a subtype of another protocol P2 if P1 defines all protocol members of P2 with compatible types. Generic protocol types follow the same rules of variance as non-protocol types. Protocol types can be used in all contexts where any other types can be used, such ...
...Type', 'return': 'float'} def foo(x = 3, y = "abc"): ... foo.__annotations__ = annotations class MyType: ... foo_y_type = foo.__annotations__['y'] This code now runs successfully. However, foo_y_type is no longer a reference to MyType, it is the string 'MyType'. The code would have to be further modified to call eval() or typing.get_type_hints() to convert the string into a useful reference to the actual MyType object. This PEP proposes a third approach, delaying the evaluation of the...
...TypedDict type can be compatible with a smaller (more general) TypedDict type. Class-based Syntax A TypedDict type can be defined using the class definition syntax with typing.TypedDict as the sole base class: from typing import TypedDict class Movie(TypedDict): name: str year: int Movie is a TypedDict type with two items: 'name' (with type str) and 'year' (with type int). A type checker should validate that the body of a class-based TypedDict definition conforms to the following rul...
...TYPE="s">pathExpr</SYMBOL> <CODE> </CODE> </RULE> <RULE> <SYMBOL TYPE="s">unionExpr</SYMBOL> <SYMBOL TYPE="s">'|'</SYMBOL> <SYMBOL TYPE="s">pathExpr</SYMBOL> <CODE> <VARIABLE TYPE="PyObject*" NAME="right"></VARIABLE> <VARIABLE TYPE="PyObject*" NAME="left"></VARIABLE> <VARIABLE TYPE="PyObject*" NAME="expr"></VARIABLE> <CODE_SNIPPE...