Object Oriented programming (OOP) problem

[OmegaRed94]

Hello everyone, Dear Pythonistas

I have started to learn python several months ago and got to Object Oriented programming (OOP), solved many exercises but some of them are still quite difficult due to the lack of examples.

The problem is the following:

Write a program that describes a function to create an object. An object is created on the basis of an already existing object that is passed to the function as an argument. Only those attributes from the original object that have an integer value are added to the new created object.

My code draft (Screenshot is attached below):

#Create arbitrary class
class Object1():
    def __init__(self,value1,value2,value3):
        self.v1=value1
        self.v2=value2
        self.v3=value3

#Create an arbitrary object
D=Object(2,3,"abc")

#Function to create a new object based on the previous 
def new_object(A):
    #Here we get keys
    a=[]
    a=list(A.__dict__.keys())

    for i in range(len(a)):
        if type(getattr(A, a[i])) != int:
            delattr(A, a[i])
    print(A.__dict__.keys())

#New object
Z=new_object(D)

In the function I checked the type of all attributes and delete those that are not integers.
In the end, it turns out that the new created object "Z" based on the object "D" has <class 'NoneType'> and doesn't have any attributes at all.
What is the problem?

Yoriz write May-31-2021, 01:03 PM:
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[BashBedlam]

Your function is not returning anything. Try it like this:

#Create arbitrary class
class Object():
	def __init__(self,value1,value2,value3):
		self.v1=value1
		self.v2=value2
		self.v3=value3

#Create an arbitrary object
D=Object(2,3,"abc")

#Function to create a new object based on the previous
def new_object(A):
	#Here we get keys
	a=[]
	a=list(A.__dict__.keys())

	for i in range(len(a)):
		if type(getattr(A, a[i])) != int:
			delattr(A, a[i])
			print(A.__dict__.keys())
	return Object (a[0], a[1], 0)

#New object
Z=new_object(D)
print (type (Z))

[jefsummers]

Your arbitrary class is named Object1, whereas D is declared to be of class Object. Add a 1.

Also that is way too close to a Python reserved word. Suggest using something like my_object so a typo like happened here is easier to pick up.

[deanhystad]

This starts with a blank class and adds attributes.

class Blank():
    pass

class NotBlank():
    def __init__(self):
        self.a = 1
        self.b = 2.0
        self.c = 'three'

def only_these_types(types, source_object):
    blank = Blank()
    for name, value in source_object.__dict__.items():
        if type(value) in types:
            setattr(blank, name, value)
    return blank


for name, value in only_these_types((int, str), NotBlank()).__dict__.items():
    print(name, value)

Something like this would only work for a "data class". The new object has none of the method attributes of the source class.

[OmegaRed94]

Your arbitrary class is named Object1, whereas D is declared to be of class Object. Add a 1.

Also that is way too close to a Python reserved word. Suggest using something like my_object so a typo like happened here is easier to pick up.

Thank you

[OmegaRed94]

Your function is not returning anything. Try it like this:

#Create arbitrary class
class Object():
	def __init__(self,value1,value2,value3):
		self.v1=value1
		self.v2=value2
		self.v3=value3

#Create an arbitrary object
D=Object(2,3,"abc")

#Function to create a new object based on the previous
def new_object(A):
	#Here we get keys
	a=[]
	a=list(A.__dict__.keys())

	for i in range(len(a)):
		if type(getattr(A, a[i])) != int:
			delattr(A, a[i])
			print(A.__dict__.keys())
	return Object (a[0], a[1], 0)

#New object
Z=new_object(D)
print (type (Z))

Thank you very much

[OmegaRed94]

This starts with a blank class and adds attributes.

class Blank():
    pass

class NotBlank():
    def __init__(self):
        self.a = 1
        self.b = 2.0
        self.c = 'three'

def only_these_types(types, source_object):
    blank = Blank()
    for name, value in source_object.__dict__.items():
        if type(value) in types:
            setattr(blank, name, value)
    return blank


for name, value in only_these_types((int, str), NotBlank()).__dict__.items():
    print(name, value)

Something like this would only work for a "data class". The new object has none of the method attributes of the source class.

Thanks