混合 Cython class 和 SqlAlchemy
Mixin Cython class and SqlAlchemy
摘要：
我有一个 cython class 代表一个业务单元。此 class 以纯 cython 样式声明。
在一个项目中，我需要将业务单元映射到数据库。为此，我想导入 .pxd 文件并使用 SQLAlchemy "map" 它。
Cython 定义
假设class装备。 class 在 .pxd 中定义了 .pyx 和 class 接口（因为我需要在其他模块中导入它）。
equipment.pxd
cdef class Equipment:
cdef readonly int x
cdef readonly str y
equipment.pyx
cdef class Equipment:
def __init__(self, int x, str y):
self.x = x
self.y = y
我编译所有内容并得到一个 equipment.pyd 文件。到目前为止，没问题。
此文件包含业务逻辑模型，不得更改。
映射
然后在一个应用程序中，我导入 equipment.pyd 并将其映射到 SQLAlchemy。
from sqlalchemy import Table, Column, Integer, String
from sqlalchemy.orm import mapper
from equipment import Equipment
metadata = MetaData()
# Table definition
equipment = Table(
'equipment', metadata,
Column('id', Integer, primary_key=True),
Column('x', Integer),
Column('y', String),
)
# Mapping the table definition with the class definition
mapper(Equipment, equipment)
TypeError: can't set attributes of built-in/extension type 'equipment.Equipment'
确实，SQLAlchemy 正在尝试创建 Equipment.c.x、Equipment.c.y，...这在 Cython 中是不可能的，因为它没有在 .pxd...
那么如何将 Cython class 映射到 SQLAlchemy？
不满意的解决方案
如果我在 .pyx 文件中以 python 模式定义设备 class，它可以工作，因为最后，它只是 'python' cython class 定义中的对象.
equipment.pyx
class Equipment:
def __init__(self, x, y):
self.x = x
self.y = y
但我失去了很多功能，这就是为什么我需要纯 Cython。
谢谢！ :-)
-- 编辑部分 --
半满意解
保留 .pyx 和 .pxd 文件。从 .pyd 继承。尝试映射。
mapping.py
from sqlalchemy import Table, Column, Integer, String
from sqlalchemy.orm import mapper
from equipment import Equipment
metadata = MetaData()
# Table definition
equipment = Table(
'equipment', metadata,
Column('id', Integer, primary_key=True),
Column('x', Integer),
Column('y', String),
)
# Inherit Equipment to a mapped class
class EquipmentMapped(Equipment):
def __init__(self, x, y):
super(EquipmentMapped, self).__init__(x, y)
# Mapping the table definition with the class definition
mapper(EquipmentMapped, equipment)
from mapping import EquipmentMapped
e = EquipmentMapped(2, 3)
print e.x
## This is empty!
为了让它工作，我必须将每个属性定义为 属性!
equipment.pxd
cdef class Equipment:
cdef readonly int _x
cdef readonly str _y
equipment.pyx
cdef class Equipment:
def __init__(self, int x, str y):
self.x = x
self.y = y
property x:
def __get__(self):
return self._x
def __set__(self, x):
self._x = x
property y:
def __get__(self):
return self._y
def __set__(self, y):
self._y = y
这并不令人满意，因为 :lazy_programmer_mode on: 我在业务逻辑中有很多更改要做... :lazy_programmer_mode off:
我认为最基本的问题是当你调用 mapper 它确实（除其他外）
Equipment.x = ColumnProperty(...) # with some arguments
Equipment.y = ColumnProperty(...)
当 ColumnProperty 是一个定义为 属性 的 sqlalchemy 时，所以当您执行 e.x = 5 时，它会注意到该值已在它周围的所有数据库相关内容中发生变化。
显然不能与您试图用来控制存储的下面的 Cython class 很好地配合。
就个人而言，我怀疑唯一真正的答案是定义一个包装器 class，它包含 Cython class 和映射的 sqlalchemy class，并拦截所有属性访问和方法调用以保持它们同步。下面是一个粗略的实现，它应该适用于简单的情况。虽然它几乎没有经过测试，所以几乎可以肯定有它遗漏的错误和极端情况。当心！
def wrapper_class(cls):
# do this in a function so we can create it generically as needed
# for each cython class
class WrapperClass(object):
def __init__(self,*args,**kwargs):
# construct the held class using arguments provided
self._wrapped = cls(*args,**kwargs)
def __getattribute__(self,name):
# intercept all requests for attribute access.
wrapped = object.__getattribute__(self,"_wrapped")
update_from = wrapped
update_to = self
try:
o = getattr(wrapped,name)
except AttributeError:
# if we can't find it look in this class instead.
# This is reasonable, because there may be methods defined
# by sqlalchemy for example
update_from = self
update_to = wrapped
o = object.__getattribute__(self,name)
if callable(o):
return FunctionWrapper(o,update_from,update_to)
else:
return o
def __setattr__(self,name,value):
# intercept all attempt to write to attributes
# and set it in both this class and the wrapped Cython class
if name!="_wrapped":
try:
setattr(self._wrapped,name,value)
except AttributeError:
pass # ignore errors... maybe bad!
object.__setattr__(self,name,value)
return WrapperClass
class FunctionWrapper(object):
# a problem we have is if we call a member function.
# It's possible that the member function may change something
# and thus we need to ensure that everything is updated appropriately
# afterwards
def __init__(self,func,update_from,update_to):
self.__func = func
self.__update_from = update_from
self.__update_to = update_to
def __call__(self,*args,**kwargs):
ret_val = self.__func(*args,**kwargs)
# for both Cython classes and sqlalchemy mappings
# all the relevant attributes exist in the class dictionary
for k in self.__update_from.__class__.__dict__.iterkeys():
if not k.startswith('__'): # ignore private stuff
try:
setattr(self.__update_to,k,getattr(self.__update_from,k))
except AttributeError:
# There may be legitmate cases when this fails
# (probably relating to sqlalchemy functions?)
# in this case, replace raise with pass
raise
return ret_val
要使用它，您需要执行以下操作：
class EquipmentMapped(wrapper_class(Equipment)):
# you may well have to define __init__ here
# you'll have to check yourself, and see what sqlalchemy does...
pass
mapper(EquipmentMapped,equipment)
请记住，这是一个可怕的解决方法，基本上只是在两个地方复制所有数据，然后拼命尝试保持同步。
编辑：这个的原始版本提供了一种机制来自动执行查询行 OP 曾尝试过但决定手动完成很多工作（在 Cython 上定义属性class，它只成功地覆盖了 sqlalchemy 的跟踪更改机制）进一步测试证实它不起作用。如果您对不该做什么感到好奇，请查看编辑历史记录！
摘要：
我有一个 cython class 代表一个业务单元。此 class 以纯 cython 样式声明。
在一个项目中，我需要将业务单元映射到数据库。为此，我想导入 .pxd 文件并使用 SQLAlchemy "map" 它。
Cython 定义
假设class装备。 class 在 .pxd 中定义了 .pyx 和 class 接口（因为我需要在其他模块中导入它）。
equipment.pxd
cdef class Equipment:
cdef readonly int x
cdef readonly str y
equipment.pyx
cdef class Equipment:
def __init__(self, int x, str y):
self.x = x
self.y = y
我编译所有内容并得到一个 equipment.pyd 文件。到目前为止，没问题。 此文件包含业务逻辑模型，不得更改。
映射
然后在一个应用程序中，我导入 equipment.pyd 并将其映射到 SQLAlchemy。
from sqlalchemy import Table, Column, Integer, String
from sqlalchemy.orm import mapper
from equipment import Equipment
metadata = MetaData()
# Table definition
equipment = Table(
'equipment', metadata,
Column('id', Integer, primary_key=True),
Column('x', Integer),
Column('y', String),
)
# Mapping the table definition with the class definition
mapper(Equipment, equipment)
TypeError: can't set attributes of built-in/extension type 'equipment.Equipment'
确实，SQLAlchemy 正在尝试创建 Equipment.c.x、Equipment.c.y，...这在 Cython 中是不可能的，因为它没有在 .pxd...
那么如何将 Cython class 映射到 SQLAlchemy？
不满意的解决方案
如果我在 .pyx 文件中以 python 模式定义设备 class，它可以工作，因为最后，它只是 'python' cython class 定义中的对象.
equipment.pyx
class Equipment:
def __init__(self, x, y):
self.x = x
self.y = y
但我失去了很多功能，这就是为什么我需要纯 Cython。
谢谢！ :-)
-- 编辑部分 --
半满意解
保留 .pyx 和 .pxd 文件。从 .pyd 继承。尝试映射。
mapping.py
from sqlalchemy import Table, Column, Integer, String
from sqlalchemy.orm import mapper
from equipment import Equipment
metadata = MetaData()
# Table definition
equipment = Table(
'equipment', metadata,
Column('id', Integer, primary_key=True),
Column('x', Integer),
Column('y', String),
)
# Inherit Equipment to a mapped class
class EquipmentMapped(Equipment):
def __init__(self, x, y):
super(EquipmentMapped, self).__init__(x, y)
# Mapping the table definition with the class definition
mapper(EquipmentMapped, equipment)
from mapping import EquipmentMapped
e = EquipmentMapped(2, 3)
print e.x
## This is empty!
为了让它工作，我必须将每个属性定义为 属性!
equipment.pxd
cdef class Equipment:
cdef readonly int _x
cdef readonly str _y
equipment.pyx
cdef class Equipment:
def __init__(self, int x, str y):
self.x = x
self.y = y
property x:
def __get__(self):
return self._x
def __set__(self, x):
self._x = x
property y:
def __get__(self):
return self._y
def __set__(self, y):
self._y = y
这并不令人满意，因为 :lazy_programmer_mode on: 我在业务逻辑中有很多更改要做... :lazy_programmer_mode off:
我认为最基本的问题是当你调用 mapper 它确实（除其他外）
Equipment.x = ColumnProperty(...) # with some arguments
Equipment.y = ColumnProperty(...)
当 ColumnProperty 是一个定义为 属性 的 sqlalchemy 时，所以当您执行 e.x = 5 时，它会注意到该值已在它周围的所有数据库相关内容中发生变化。
显然不能与您试图用来控制存储的下面的 Cython class 很好地配合。
就个人而言，我怀疑唯一真正的答案是定义一个包装器 class，它包含 Cython class 和映射的 sqlalchemy class，并拦截所有属性访问和方法调用以保持它们同步。下面是一个粗略的实现，它应该适用于简单的情况。虽然它几乎没有经过测试，所以几乎可以肯定有它遗漏的错误和极端情况。当心！
def wrapper_class(cls):
# do this in a function so we can create it generically as needed
# for each cython class
class WrapperClass(object):
def __init__(self,*args,**kwargs):
# construct the held class using arguments provided
self._wrapped = cls(*args,**kwargs)
def __getattribute__(self,name):
# intercept all requests for attribute access.
wrapped = object.__getattribute__(self,"_wrapped")
update_from = wrapped
update_to = self
try:
o = getattr(wrapped,name)
except AttributeError:
# if we can't find it look in this class instead.
# This is reasonable, because there may be methods defined
# by sqlalchemy for example
update_from = self
update_to = wrapped
o = object.__getattribute__(self,name)
if callable(o):
return FunctionWrapper(o,update_from,update_to)
else:
return o
def __setattr__(self,name,value):
# intercept all attempt to write to attributes
# and set it in both this class and the wrapped Cython class
if name!="_wrapped":
try:
setattr(self._wrapped,name,value)
except AttributeError:
pass # ignore errors... maybe bad!
object.__setattr__(self,name,value)
return WrapperClass
class FunctionWrapper(object):
# a problem we have is if we call a member function.
# It's possible that the member function may change something
# and thus we need to ensure that everything is updated appropriately
# afterwards
def __init__(self,func,update_from,update_to):
self.__func = func
self.__update_from = update_from
self.__update_to = update_to
def __call__(self,*args,**kwargs):
ret_val = self.__func(*args,**kwargs)
# for both Cython classes and sqlalchemy mappings
# all the relevant attributes exist in the class dictionary
for k in self.__update_from.__class__.__dict__.iterkeys():
if not k.startswith('__'): # ignore private stuff
try:
setattr(self.__update_to,k,getattr(self.__update_from,k))
except AttributeError:
# There may be legitmate cases when this fails
# (probably relating to sqlalchemy functions?)
# in this case, replace raise with pass
raise
return ret_val
要使用它，您需要执行以下操作：
class EquipmentMapped(wrapper_class(Equipment)):
# you may well have to define __init__ here
# you'll have to check yourself, and see what sqlalchemy does...
pass
mapper(EquipmentMapped,equipment)
请记住，这是一个可怕的解决方法，基本上只是在两个地方复制所有数据，然后拼命尝试保持同步。
编辑：这个的原始版本提供了一种机制来自动执行查询行 OP 曾尝试过但决定手动完成很多工作（在 Cython 上定义属性class，它只成功地覆盖了 sqlalchemy 的跟踪更改机制）进一步测试证实它不起作用。如果您对不该做什么感到好奇，请查看编辑历史记录！