I am trying to understand whether declaring variables inside constructors is an ok practice. I only need these variables inside the constructor. I am asking this because most of the times I've seen constructors they only contained self variables. I've tried to find an answer on the internet but had no luck.
Here is an example code
class Patient:
def __init__(self, all_images_path: str):
all_patient_images = os.listdir(all_images_path)
all_patient_images = [(all_images_path + x) for x in all_patient_images if 'colourlay' in x]
self.images: [Image] = [Image.open(img_path) for img_path in all_patient_images]
Is there anything wrong with the above code? If yes, what? Thank you!
From a design standpoint, Patient.__init__ is doing too much. I would keep __init__ as simple as possible:
class Patient:
def __init__(self, images: list[Image]):
self.images = images
The caller of __init__ is responsible for producing that list of Image values. However, that doesn't mean your user is the one calling __init__. You can define a class method to handle the messy details of extracting images from a path, and calling __init__. (Note it gets less messy if you use the pathlib module.)
from pathlib import Path
class Patient:
def __init__(self, images: list[Image]):
self.images = images
@classmethod
def from_path(cls, all_images_path: Path):
files = all_images_path.glob('*colourlay*')
return cls([Image.open(f) for f in files])
Note that Image itself seems to take this approach: you aren't constructing an instance of Image directly, but using a class method to extract the image data from a file.