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python: set read-only attribute for class objects


python: set read-only attribute for class objects

By : foEs
Date : November 21 2020, 07:38 AM
help you fix your problem I've created a class object called 'Node'. I then created two subclasses 'Beetle' and 'Dakota'. You'll notice there is an attr called 'superclass' which is part of the baseclass. I want this attribute to be set for each subclass and once it's set it should never be changed. It's a read-only attribute. I was wondering how to set this attribute up correctly in order to be a read only attribute? , Rename you variable to add __ to the begining
code :
self.__superclass = superclass
def getsuperclass(self):
    return self.__superclass
...

Dakota().getsuperclass()


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How do I find objects from child class by attribute in Python

How do I find objects from child class by attribute in Python


By : Josh Peck
Date : March 29 2020, 07:55 AM
around this issue Your inheritance make no sense. Buildings are not rectangles, and rectangles are not points. This is a job for composition, not inheritance, and you're correctly doing that by passing in the points etc - just leave off the inheritance.
Apart from that, I'm not sure what your question is. There's no way to query attributes other than iterating through, which you're already doing, unless you store then in some kind of data structure that indexes the attribute you want to query.
Python Class Objects Attribute Referencing

Python Class Objects Attribute Referencing


By : ServerSteam
Date : March 29 2020, 07:55 AM
I wish did fix the issue. I have two classes. a and b. , This works:
code :
class b:
    def __init__(self):
        self.attribute_function = None

class a:
    def __init__(self):
        self._temp = 10
        self.counter = 0

    def temp(self):
        obj = b()
        obj.attribute_function = lambda self=self: self.counter < self._temp
        return obj.attribute_function()


if __name__ == "__main__":
    obj = a()
    print obj.temp()
class B:
    def __init__(self, a):
        self.a = a
    def temp(self):
        return self.a.temp()

class A:
    def __init__(self):
        self._temp = 10
        self.counter = 0

    def temp(self):
        return self.counter < self._temp


if __name__ == "__main__":
    obj = B(A())
    print obj.temp()
Extracting class attribute from objects in non class array in python

Extracting class attribute from objects in non class array in python


By : Carriedee Meier
Date : March 29 2020, 07:55 AM
Any of those help I solved this by assigning each direction to the class and then using the appropriate identifier to call the portion required.
code :
class Direction:
def __init__(self, array, dir_name):
    self.array = array
    self.dir_name = dir_name      

L = Direction(L, 'L')
R = Direction(R, 'R')
U = Direction(U, 'U')
D = Direction(D, 'D')

Arrow_Array = [L.array, R.array, U.array, D.array]
num_seq = 2910
ArrSequence = [0]*num_seq

for i in range(num_seq):
    name = []    
    Arr_Seq = get_arrow_seq(6)
    for i in range(len(Arr_Seq)):     
        if (Arr_Seq[i] == L.array).all():
            name.append('L')
        elif (Arr_Seq[i] == R.array).all():
            name.append('R')
        elif (Arr_Seq[i] == U.array).all():
            name.append('U') 
        elif (Arr_Seq[i] == D.array).all():
            name.append('D')
        else:
            name.append(0)
    if i<2:  
        ArrSequence[i] = np.hstack(Arr_Seq) 

    elif np.hstack(Arr_Seq) not in [ArrSequence]:
        ArrSequence[i] = np.hstack(Arr_Seq)  

    else:
        i = i-1   

    cv2.imwrite(''.join(name) + '.png', ArrSequence[i])
Python attribute that is read only within class

Python attribute that is read only within class


By : 黃國欽
Date : March 29 2020, 07:55 AM
wish help you to fix your issue As opposed to other (commonly used) programming languages Python comes with a new approach regarding accessing class/instance members. For example, nothing is really private, the fields/methods that:
start with an _, are regular fields start with __ (and end with at most one _), are just name mangled, but they still can be accessed (even modified/deleted) from outside the class
code :
class LockedAttribute(object):
    def __init__(self, name):
        self._name = name
        self._set_count = 0
        self._set_treshold = 1

    def __get__(self, instance, cls):
        return instance.__dict__[self._name]

    def __set__(self, instance, value):
        if self._set_count >= self._set_treshold:
            raise AttributeError("Can't set attribute '{}'".format(self._name))
        else:
            instance.__dict__[self._name] = value
            self._set_count += 1

    def __delete__(self, instance):
        raise AttributeError("Can't delete attribute '{}'".format(self._name))


class GenericStrategy(object):
    portfolio = LockedAttribute("portfolio")

    def __init__(self, portfolio):
        self.portfolio = portfolio
        try:
            self.portfolio = portfolio
        except AttributeError as e:
            print("  ERROR: {}".format(e))

    def set_portfolio(self, new_value):
        self.portfolio = new_value


if __name__ == "__main__":
    strategy = GenericStrategy("some portfolio name")
    print("Portfolio: {}".format(strategy.portfolio))
    try:
        del strategy.portfolio
    except AttributeError as e:
        print("  ERROR: {}".format(e))
    try:
        strategy.set_portfolio("some 2nd portfolio name")
    except AttributeError as e:
        print("  ERROR: {}".format(e))
    try:
        strategy.portfolio = "some 3rd portfolio name"
    except AttributeError as e:
        print("  ERROR: {}".format(e))
    print("Portfolio: {}".format(strategy.portfolio))
How to determine if a Python class attribute is read only/writeable?

How to determine if a Python class attribute is read only/writeable?


By : Rakhmanov Ivan
Date : March 29 2020, 07:55 AM
I wish this helpful for you Most names will be settable by default. The exceptions are the data descriptor objects and classes that define the __setattr__ hook.
A data descriptor is any attribute of the class that has a __get__ method and at least either a __set__ or a __delete__ method. These methods are used when you try to set or delete the attribute on an instance of the class.
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