在Python中将functools.partial设置为实例方法
我正在使用在Python中将functools.partial设置为实例方法,python,class,methods,closures,Python,Class,Methods,Closures,我正在使用functools.partial创建闭包,并使用setattr从类实例调用make。这里的想法是在运行时创建一组方法 #!/usr/bin/python from functools import partial class MyClass(object): def __init__(self, val): self.val = val @classmethod def generateMethods(self): def
functools.partial
创建闭包,并使用setattr
从类实例调用make。这里的想法是在运行时创建一组方法
#!/usr/bin/python
from functools import partial
class MyClass(object):
def __init__(self, val):
self.val = val
@classmethod
def generateMethods(self):
def dummy(conf1, self):
print "conf1:", conf1
print "self.val:", self.val
print
for s in ('dynamic_1', 'dynamic_2'):
closed = partial(dummy, s)
setattr(self, "test_{0}".format(s), closed)
在我看来,partial
会将s
的当前值绑定到dummy
的第一个参数,这将释放self
以在从实例调用时传递
这不是我所期望的那样
if __name__ == '__main__':
# Dynamically create some methods
MyClass.generateMethods()
# Create an instance
x = MyClass('FOO')
# The dynamically created methods aren't callable from the instance :(
#x.test_dynamic_1()
# TypeError: dummy() takes exactly 2 arguments (1 given)
# .. but these work just fine
MyClass.test_dynamic_1(x)
MyClass.test_dynamic_2(x)
是否可以动态创建闭包方法,但可以从类的实例调用这些方法?问题是,当您使用实例调用它们时,它们实际上不是绑定方法,即它们不知道该实例。绑定方法在调用时自动将
self
插入到基础函数的参数中,它存储在绑定方法的\uuuuuuuuuuuuuuuuuuuuuuuu
属性中
因此,重写并查看正在获取的对象是否是partial
类型的实例,如果是,则使用将其转换为绑定方法
代码:
#!/usr/bin/python
from functools import partial
import types
class MyClass(object):
def __init__(self, val):
self.val = val
@classmethod
def generateMethods(self):
def dummy(conf1, self):
print "conf1:", conf1
print "self.val:", self.val
print
for s in ('dynamic_1', 'dynamic_2'):
closed = partial(dummy, s)
setattr(self, "test_{0}".format(s), closed)
def __getattribute__(self, attr):
# Here we do have access to the much need instance(self)
obj = object.__getattribute__(self, attr)
if isinstance(obj, partial):
return types.MethodType(obj, self, type(self))
else:
return obj
if __name__ == '__main__':
MyClass.generateMethods()
x = MyClass('FOO')
x.test_dynamic_1()
x.test_dynamic_2()
我认为新的是为了这个确切的用例
直接从文档中:
>>> class Cell(object):
... def __init__(self):
... self._alive = False
... @property
... def alive(self):
... return self._alive
... def set_state(self, state):
... self._alive = bool(state)
... set_alive = partialmethod(set_state, True)
... set_dead = partialmethod(set_state, False)
...
>>> c = Cell()
>>> c.alive
False
>>> c.set_alive()
>>> c.alive
True
可能重复@alfasin,该问题询问如何向特定实例添加方法;我的问题是关于向类中添加方法的问题,这些方法将由所有instancesTrue继承,但公认的答案显示了如何完成这两项工作!我想没有办法立即将闭包添加为
MethodType
,而不是在调用时动态转换它?