Python - classes

# Define a class to hold a satellite or aerial imagery file. Its properties give information
# such as location of the ground, area, dimensions, spatial and spectral resolution etc.

class ImageryObject:
    _default_gsd = 5.0
    
    def __init__(self, file_path):
        self._file_path = file_path
        self._gps_location = (3,4)
        
    @property
    def bands(self):
        #count number of bands
        count = 3
        return count
    
    @property
    def gsd(self):
        # logic to calculate the ground sample distance
        gsd = 10.0
        return gsd
    
    @property
    def address(self):
        # logic to reverse geocode the self._gps_location to get address
        # reverse geocode self._gps_location
        address = "123 XYZ Street"
        return address
    
    #class methods
    def display(self):
        #logic to display picture
        print("image is displayed")
    
    def shuffle_bands(self):
        #logic to shift RGB combination
        print("shifting pands")
        self.display()

# class instantiation
img1 = ImageryObject("user\img\file.img") #pass value to constructor

img1.address

img1._default_gsd

img1._gps_location

img1.shuffle_bands()

# Get help on any object. Only public methods, properties are displayed.
# fields are private, properties are public. Class variables beginning with _ are private fields.
help(img1)

class Rectangle:
    "Defines a rectangle"
    
    def __init__(self, width, height):
        self._width = width
        self._height = height
        
    @property
    def width(self):
        return self._width
    
    @width.setter
    def width(self, w):
        if w < 0:
            raise ValueError("Width cannot be negative")
        else:
            self._width = w
    
    @property
    def height(self):
        return self._height
    
    @height.setter
    def height(self, h):
        if h < 0:
            raise valueError("Height cannot be negative")
        else:
            self._height = h
    
    def area(self):
        return self._width * self._height
    
    def perimeter(self):
        return 2*(self._width + self._height)
    
    # Customize how the object prints
    def __str__(self):
        return f"Rectangle: Width: {self._width}  Height: {self._height}"
    
    # Customize how the object displays in IPython kernels like notebooks
    def _repr_png_(self):
        import matplotlib.pyplot as plt
        from matplotlib.patches import Rectangle
        
        #define Matplotlib figure and axis
        fig, ax = plt.subplots()
        
        #create simple line plot
        ax.plot([0, 10],[0, 10])


        #add rectangle to plot
        ax.add_patch(Rectangle((1, 1), self._width, self._height))

        #display plot
        # plt.show()
        return ax
    
    # Equality checks. 
    # If you compare r1=Rectangle(10, 20) and r2 = Rectangle(10, 20), they would 
    # r1 is r2 => will return false as it should. These are 2 different objects
    # r1 == r2 => will also return False
    def __eq__(self, other):
        if isinstance(other, self.__class__):
            if self.width == other.width and self.height == other.height:
                return True
            
        return False
    
    # LT, GT, LE, GE comparisons
    def __le__(self, other):
        if isinstance(other, self.__class__):
            if self.area() <= other.area():
                return True
        
        return False

r1 = Rectangle(10, 20)
print(r1)
r1

r1.area(), r1.perimeter()

r2 = Rectangle(10, 20) # same as r1
r1 is r2  # should be false as these are two diff obj, not singleton with alias

r1 == r2  # This should equate to True as these are the identical objects

r1 <= r2

r3 = Rectangle(30, 40)
print(r1 <= r3)
print(r3 <= r1)

r2 >= r3  # even though ge is not implemented, Python is smart and will flip le and use it.

# Will throw an error:
r2 > r3

print(None is None)
print(None == None)

lupus = None
print(lupus is None)  # Evals to True as None is a singleton and lupus is an alias
print(lupus == None)