can u do some logic in init of a class?

Question

okay, some background, i was mainly using imperative and functional programming for last couple of years … now i’m learning OOP and i feel that my code not following the best practices of the OOP paradigm.

class ImageBounding(Bounding):

def __init__(self, x, y, w, h, image):
    super().__init__(x, y, w, h)
    self.image = image
    img = Image.fromarray(self.image)
    self.text = pytesseract.image_to_string(img)

well i want text to be an attribute of any instance of ImageBounding but text depends on the value of the attribute image … it’s working but i feel the way i wrote this something is wrong.

please enlighten me if you know how to do this in a better way,

Asked By: youssef

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Source

Answer 1

You can, but it might be better to minimize it. For example, the "dumbest" version of __init__ would simply take an existing image and its corresponding text. A class method could be used to encapsulate the logic that derives text from the image.

class ImageBounding(Bounding):
    
    def __init__(self, x, y, w, h, image, text):
        super().__init__(x, y, w, h)
        self.image = image
        self.text = text

    @classmethod
    def from_image(cls, x, y, w, h, image):
        text = pytesseract.image_to_string(Image.fromarray(image))
        return cls(x, y, w, h, image, text)

Note that this is similar to how Image itself is defined; Image.fromarray is (probably) a class method like

def fromarray(cls, img):
    t = do_something_with_image(img)
    return cls(t)

This allows the creation of an ImageBounding instance to be easier (and potentially cheaper) for testing, without sacrificing the ability to create a "properly" configured instance in practice.

Answered By: chepner

Answer 2

while this works and as an example seems fine you could do either of the following:

just process the image outside of the class and pass it to the constructor afterwards or

create a private method to do the processing and call it from within __init__

class ImageBounding(Bounding):

 def __init__(self, x, y, w, h, image):
     super().__init__(x, y, w, h)
     self.image = image
     self.text = self._processed_image()

 def _processed_image(self)
     img = Image.fromarray(self.image)
     return pytesseract.image_to_string(img)

Answered By: vencaslac

can u do some logic in init of a class?

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can u do some logic in __init__ of a class?

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can u do some logic in init of a class?