目标(在python2.7中):
检查任意对象,找到所有实例变量。但排除类变量。在
最终目标:
从没有提供有用的“str”实现的第三方类库打印对象的有用细节。(Maya的PythonAPI,版本1,是一个简单的SWIG包装器。 不使用版本2,因为我正在学习一些版本1的示例。)
示例类:
# ---------- class Vector ----------
class Vector(object):
def __init__(self, x=0.0, y=0.0, z=0.0):
self.x, self.y, self.z = x, y, z
# Provide useful info for 'repr(self)', 'str(self)', and 'print self'.
def __repr__(self):
return 'Vector({0}, {1}, {2})'.format(self.x, self.y, self.z)
# math operators
def __add__(self, other):
return Vector(self.x + other.x, self.y + other.y, self.z + other.z)
# a simple method
def ApproximateLength(self):
return self.x + self.y + self.z
# list/sequence/iterator support.
def tolist(self):
return [self.x, self.y, self.z]
def __len__(self):
return 3
# No need for "next(self)", because we create a list, use its iterator.
def __iter__(self):
return iter(self.tolist())
# class variable
Vector.Zero = Vector()
目前的解决方案:
^{pr2}$用法示例:
vec = Vector(1.0, 2.0, 3.0)
printElements(Attributes(vec))
输出:
('Zero', Vector(0.0, 0.0, 0.0))
('x', 1.0)
('y', 2.0)
('z', 3.0)
这个类本身打印得很好:
print vec
=>
Vector(1.0, 2.0, 3.0)
目标是提取相似的信息,对于那些我没有源代码(或者不想修改源代码)的类。这些类有许多类变量,这些变量隐藏了我所寻找的信息。在
问题:
如何检测“0”是从Vector继承的“类变量”,以便从输出中消除它?在
如果没有更好的方法,我将使用笨拙的方法:
printElements(Attributes(type(vec)))
列出对象类型的属性。可以对照“type(vec)”的属性测试“vec”的每个属性,不包括任何匹配的属性。我不关心类和实例上存在相同命名属性的微妙可能性。所以这可以满足我的要求。在
然而,这似乎有些笨拙。有没有更直接的方法来确定属性是否是从类继承的?在
编辑:结合乔兰的回答:
def IsClassVar(self, attrName):
return hasattr(self.__class__, attrName)
def Attributes(ob):
....
publicAttributes = filter(lambda desc: Public(desc[0]), attributes)
# Exclude 'class' variables.
# NOTE: This does not attempt to detect whether the instance variable is different than the class variable.
publicAttributes = filter(lambda desc: not isClassVar(ob, desc[0]), publicAttributes)
return publicAttributes
这将产生所需的结果:
printElements(Attributes(vec))
=>
('x', 1.0)
('y', 2.0)
('z', 3.0)
或者,检测实例变量覆盖类变量:
def IsClassVar(self, attrName):
return hasattr(self.__class__, attrName)
# REQUIRE attrName already known to be supported by self.
# But just in case, return False if exception, so will be skipped.
def IsNotSameAsClassVar(self, attrName):
try:
if not IsClassVar(self, attrName):
return True
# If it has different value than class' attribute, it is on the instance.
return getattr(self, attrName) is not getattr(self.__class__, attrName)
except:
return False
def Attributes(ob):
....
publicAttributes = filter(lambda desc: Public(desc[0]), attributes)
# Exclude 'class' variables.
# More complete solution.
publicAttributes = filter(lambda desc: IsNotSameAsClassVar(ob, desc[0]), publicAttributes)
return publicAttributes
现在,如果我们覆盖vec上的'Zero',它将包括:
# Probably a bad idea, but showing the principle.
vec.Zero = "Surprise!"
然后:
print vec.Zero
print Vector.Zero
=>
Surprise!
Vector(0.0, 0.0, 0.0)
以及:
printElements(Attributes(vec))
=>
('Zero', 'Surprise!')
('x', 1.0)
('y', 2.0)
('z', 3.0)
像这样的事情可能会奏效
注意,这并不一定意味着它是一个实例变量。。。只是那不是一个类变量
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