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Dynamic python properties


Dynamic python properties

By : user2955172
Date : November 22 2020, 10:38 AM
around this issue Given the question "Can instances of MyClass each have unique getter/setter functions for property y?", the literal answer is "no" -- descriptors (including property) are looked up on the class, not on the instance.
However, class-level descriptors can delegate to instance-held callables, resulting in a similar effect. Your example is not fully clear to me, but, consider for example:
code :
class Whatever(object):

    def __init__(self, scale, getter=lambda x: 42):
        self.scale = scale
        self.getter = getter

    @property
    def y(self):
        return self.getter(self.scale)

plain = Whatever(33)
fancy = Whatever(47, lambda x: x*2)
class MyHelper:
    def __init__(self, label):
        self.mylabel = label

    def getter2(self, other):
        return other.mydict[self.mylabel]

    def setter2(self, other, value):
        other.mydict[self.mylabel] = value

def makeProperty(label):
    H = MyHelper(label)
    return property(H.getter2, H.setter2)

class MyClass:
    def __init__(self, d):
        self.mydict = d

    X = makeProperty('X')
    Y = makeProperty('Y')


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Python passing in a list of parameters to be used as dynamic properties

Python passing in a list of parameters to be used as dynamic properties


By : worldservice828
Date : March 29 2020, 07:55 AM
will be helpful for those in need You can't have per-instance properties (or at least not without messing with get_attribute, which is something you really should avoid). The simplest solution is to use getattr.
code :
class MultipleMacroFor(object):
    def __init__(self, macro, names):
        self._macro = macro
        self._names = names

    def get_renderable(self, macro_var):
        return get_template_attribute(self.macro, macro_var)

    def __getattr__(self, name):
        if name in self._names:
            return self.get_renderable(name)
        raise AttributeError(
            "object %s has no attribute '%s'" % (
                type(self).__name__, name)
            )
class MultipleMacroFor(object):
    def __init__(self, macro, names):
        self._macro = macro
        self._names = names


    def get_renderable(self, macro_var):
        return get_template_attribute(self.macro, macro_var)

def MultipleMacroForFactory(macro, names):
    attrs = dict()
    for name in names:
        attrs[name] = property(
            lambda self, name=name: self.get_renderable(name)
            )

    clsname = "MultipleMacroFor%s" % "".join(
        name.capitalize() for name in names
        )

    return type(clsname, (MultipleMacroFor,), attrs)(macro, names)
Python extremely dynamic class properties

Python extremely dynamic class properties


By : Paula Martins
Date : March 29 2020, 07:55 AM
help you fix your problem These are called attributes, rather than properties. With that in mind, the method setattr() becomes more obvious:
code :
class Foo(object):
    def __init__(self, l):
        for k, v in l:
            setattr(self, k, v)
l = [("first","foo"),("second","bar"),("anything","you get the point")]
bar = Foo(l)

print bar.first
#foo
print bar.second
#bar
print bar.anything
#you get the point
Dynamic lazy class properties python

Dynamic lazy class properties python


By : Arbalest
Date : March 29 2020, 07:55 AM
will be helpful for those in need I have a class, Record, that is used to contain the results of reading text file. The file contains a simple database with fields and tags. I would like to have each Record instance only have the properties associated with its database. Basically: , I have a solution that seems to work although it is quite ugly:
code :
class Record(object):
   def __init__(self, file):
     self._unComputedTags = set() #needs to be initialized first
      #stuff
      self._unComputedTags = set(self._fieldDict.keys())
      for tag in self._fieldDict:
            self.__dict__[tag] = None

   def __getattribute__(self, name):
       if name == '_unComputedTags':
           #This may be unnecessary if I play with things a bit
           return object.__getattribute__(self, '_unComputedTags')
       if name in self._unComputedTags:
           try:
               tagVal = tagToFunc[name](self._fieldDict[name])
           except KeyError:
               tagVal = self._fieldDict[name]
           setattr(self, name, tagVal)
           self._unComputedTags.remove(name)
       return object.__getattribute__(self, name)
Python dynamic properties and mypy

Python dynamic properties and mypy


By : Liang.Q
Date : March 29 2020, 07:55 AM
wish help you to fix your issue Fix your IDE? :-). In Python there will always be corner cases where static analysis can't go . In this case you got the tools that ere supposed to be helping you getting in your way.
There is no way for either the IDE or Mypy to find about these dynamic attributes without running the code. I know there are IDEs, that at least in the past, resorted to actually importing a module to have auto-complete - but that also can trigger a host of collateral effects.
Python-Gstreamer for dynamic control of element properties

Python-Gstreamer for dynamic control of element properties


By : David Merrill
Date : March 29 2020, 07:55 AM
it helps some times The problem here is that the gltransformation properties are not controllable. i.e. they don't have the GST_PARAM_CONTROLLABLE flag on property creation in the code.
You can either add controllability to gltransformation by proposing a patch upstream or not relying on controllable properties.
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