8.9. types — 动态类型创建和内置类型名称 ¶

8.9.1. 动态类型创建 ¶

types. new_class ( name , bases=() , kwds=None , exec_body=None ) ¶

Creates a class object dynamically using the appropriate metaclass.

The first three arguments are the components that make up a class definition header: the class name, the base classes (in order), the keyword arguments (such as metaclass ).

exec_body argument is a callback that is used to populate the freshly created class namespace. It should accept the class namespace as its sole argument and update the namespace directly with the class contents. If no callback is provided, it has the same effect as passing in lambda ns: ns .

3.3 版新增。

types. prepare_class ( name , bases=() , kwds=None ) ¶

Calculates the appropriate metaclass and creates the class namespace.

The arguments are the components that make up a class definition header: the class name, the base classes (in order) and the keyword arguments (such as metaclass ).

The return value is a 3-tuple: metaclass, namespace, kwds

metaclass is the appropriate metaclass, namespace is the prepared class namespace and kwds is an updated copy of the passed in kwds argument with any 'metaclass' entry removed. If no kwds argument is passed in, this will be an empty dict.

3.3 版新增。

3.6 版改变： The default value for the namespace element of the returned tuple has changed. Now an insertion-order-preserving mapping is used when the metaclass does not have a __prepare__ method,

8.9.2. 标准解释器类型 ¶

This module provides names for many of the types that are required to implement a Python interpreter. It deliberately avoids including some of the types that arise only incidentally during processing such as the listiterator 类型。

Typical use of these names is for isinstance() or issubclass() checks.

Standard names are defined for the following types:

types. FunctionType ¶

types. LambdaType ¶

The type of user-defined functions and functions created by lambda expressions.

types. GeneratorType ¶

The type of generator -iterator objects, created by generator functions.

types. CoroutineType ¶

The type of 协程 objects, created by async def 函数。

3.5 版新增。

types. AsyncGeneratorType ¶

The type of 异步生成器 -iterator objects, created by asynchronous generator functions.

3.6 版新增。

types. CodeType ¶

The type for code objects such as returned by compile() .

types. MethodType ¶

The type of methods of user-defined class instances.

types. BuiltinFunctionType ¶

types. BuiltinMethodType ¶

The type of built-in functions like len() or sys.exit() , and methods of built-in classes. (Here, the term “built-in” means “written in C”.)

class types. ModuleType ( name , doc=None ) ¶

The type of 模块 . Constructor takes the name of the module to be created and optionally its docstring .

注意

使用 importlib.util.module_from_spec() to create a new module if you wish to set the various import-controlled attributes.

__doc__ ¶

docstring of the module. Defaults to None .

__loader__ ¶

loader which loaded the module. Defaults to None .

3.4 版改变： 默认为 None . Previously the attribute was optional.

__name__ ¶

The name of the module.

__package__ ¶

Which package a module belongs to. If the module is top-level (i.e. not a part of any specific package) then the attribute should be set to '' , else it should be set to the name of the package (which can be __name__ if the module is a package itself). Defaults to None .

3.4 版改变： 默认为 None . Previously the attribute was optional.

types. TracebackType ¶

The type of traceback objects such as found in sys.exc_info()[2] .

types. FrameType ¶

The type of frame objects such as found in tb.tb_frame if tb is a traceback object.

types. GetSetDescriptorType ¶

The type of objects defined in extension modules with PyGetSetDef ，譬如 FrameType.f_locals or array.array.typecode . This type is used as descriptor for object attributes; it has the same purpose as the property type, but for classes defined in extension modules.

types. MemberDescriptorType ¶

The type of objects defined in extension modules with PyMemberDef ，譬如 datetime.timedelta.days . This type is used as descriptor for simple C data members which use standard conversion functions; it has the same purpose as the property type, but for classes defined in extension modules.

CPython 实现细节： In other implementations of Python, this type may be identical to GetSetDescriptorType .

class types. MappingProxyType ( 映射 ) ¶

Read-only proxy of a mapping. It provides a dynamic view on the mapping’s entries, which means that when the mapping changes, the view reflects these changes.

3.3 版新增。

key in proxy

返回 True if the underlying mapping has a key key ，否则 False .

proxy[key]

Return the item of the underlying mapping with key key 。引发 KeyError if key is not in the underlying mapping.

iter(proxy)

Return an iterator over the keys of the underlying mapping. This is a shortcut for iter(proxy.keys()) .

len(proxy)

Return the number of items in the underlying mapping.

copy ( ) ¶

Return a shallow copy of the underlying mapping.

get ( key [ , default ] ) ¶

返回值为 key if key is in the underlying mapping, else default 。若 default 不给定，它默认为 None ，因此此方法从不引发 KeyError .

items ( ) ¶

Return a new view of the underlying mapping’s items ( (key, value) pairs).

keys ( ) ¶

Return a new view of the underlying mapping’s keys.

values ( ) ¶

Return a new view of the underlying mapping’s values.

8.9.3. 额外实用类和函数 ¶

class types. SimpleNamespace ¶

A simple object subclass that provides attribute access to its namespace, as well as a meaningful repr.

不像 object ，采用 SimpleNamespace you can add and remove attributes. If a SimpleNamespace object is initialized with keyword arguments, those are directly added to the underlying namespace.

The type is roughly equivalent to the following code:

class SimpleNamespace:
    def __init__(self, **kwargs):
        self.__dict__.update(kwargs)
    def __repr__(self):
        keys = sorted(self.__dict__)
        items = ("{}={!r}".format(k, self.__dict__[k]) for k in keys)
        return "{}({})".format(type(self).__name__, ", ".join(items))
    def __eq__(self, other):
        return self.__dict__ == other.__dict__
										

SimpleNamespace may be useful as a replacement for class NS: pass . However, for a structured record type use namedtuple() 代替。

3.3 版新增。

types. DynamicClassAttribute ( fget=None , fset=None , fdel=None , doc=None ) ¶

Route attribute access on a class to __getattr__.

This is a descriptor, used to define attributes that act differently when accessed through an instance and through a class. Instance access remains normal, but access to an attribute through a class will be routed to the class’s __getattr__ method; this is done by raising AttributeError.

This allows one to have properties active on an instance, and have virtual attributes on the class with the same name (see Enum for an example).

3.4 版新增。

8.9.4. 协程实用函数 ¶

types. 协程 ( gen_func ) ¶

This function transforms a generator function into a 协程函数 which returns a generator-based coroutine. The generator-based coroutine is still a 生成器迭代器 , but is also considered to be a 协程 object and is awaitable . However, it may not necessarily implement the __await__() 方法。

若 gen_func is a generator function, it will be modified in-place.

若 gen_func is not a generator function, it will be wrapped. If it returns an instance of collections.abc.Generator , the instance will be wrapped in an awaitable proxy object. All other types of objects will be returned as is.

3.5 版新增。