How to create an object of a certain class by dynamically passing only one (perhaps multiple but not all) parameters?

Question

Let's say I have the following class.

class A:
    def __init__(self, x=0, y=0):
        self.x = x
        self.y = y

obj_A = A(y=2) # Dynamically pass the parameters

My question is, how can I dynamically create an object of a certain class by passing only one (perhaps multiple but not all) parameters? Also, I have prior knowledge of the attributes name i.e. 'x' and 'y' and they all have a default value.

Edit: To clear up some confusion. The class can have any number of attributes. Is it possible to create an instance by passing any subset of the parameters during runtime?

I know I can use getters and setters to achieve this, but I'm working on OpenCV python, and these functions are not implemented for some algorithms.

It's a little unclear what you are looking for. In your code, obj_A is an instance of class A. With y as 2 and x set to 0. Isn't that what you want? — Mark
– Mark, Commented May 18, 2020 at 1:53

DarrylG · Accepted Answer · 2020-05-18 02:15:16Z

0

Using Approach

Code

import functools

class A:
    def __init__(self, x=0, y=0):
        self.x = x
        self.y = y

    def __str__(self):
      return f'x:{self.x}, y:{self.y}'  # added to see instance data

def partialclass(cls, *args, **kwds):

    class NewCls(cls):
        __init__ = functools.partialmethod(cls.__init__, *args, **kwds)

    return NewCls

Test

# Create Partial Class (setting x only)
A_init = partialclass(A, x=3.14159)

# Setting y dynamically
# Create instance from A_init by setting y
a_2 = A_init(y=2)
print(a_2)  # Out: x:3.14159, y:2

# Create instance from A_init using y default
a_default = A_init()   
print(a_default)       # Out: x:3.14159, y:0

answered May 18, 2020 at 2:15

DarrylG

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Comments

111Seven · Accepted Answer · 2020-05-18 02:20:04Z

0

I am guessing you are looking for dynamic class creation. If so, you should use type(name,bases,dict).

check this previous strackoverflow thread

answered May 18, 2020 at 2:20

111Seven

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