class Rectangle

class Rectangle:
    color = 'red'
    def __init__(self, width, height):
        self.width = width  #self is the object which is to be filled in later outside the class, like r1, r2.
        self.height = height #there is 2 empty columns named as width, and height.
    
    def area(self):
        return self.width * self.height
        
    def perimeter(reference_object): #reference_object here is like "self" in area's self. self can be named as anything you want
        return 2 *(reference_object.width + reference_object.height)
        
#    def to_string(self):
#       return "Rectangle (width={0}, height={1})".format(self.width, self.height)
    def __str__(self): # write a __str__ to replace the __str__ inside python
        return "Rectangle (width={0}, height={1})".format(self.width, self.height)
        
    def __repr__(self): # write a __str__ to replace the __str__ inside python
        return "Rectangle({0}, {1})".format(self.width, self.height)
        
    def __eq__(self, other): #function to compare width and height, equal
        print('self ={0}, other ={1}'.format(self, other))
        if isinstance(other, Rectangle): 
            return (self.width, self.height) == (other.width, other.height)
        else:
            return False
    
    def __lt__(self, other): #function to check less than to overwrite the internal function __lt__
        if isinstance(other, Rectangle): #check other is an instance of Rectangle
            return (self.area() < other.area())
        else:
            return NotImplemented #not the same as False, false has some meaning of comparision. 
#NotImplemented compute the value of "none" something like that
#here, by using NotImplemented, if the result of r1 < r2 is false, the other side by ">" will be computed again to check if r2 > r1.

r1 = Rectangle(10, 20) #width = 10, height = 20 for r1. or say, r1.width = 10, r1.height = 20. r1 is an object of Rectangle
r2 = Rectangle(10, 20)    #width = 3, height = 5 for r2. or say r2.width = 3, r2.height = 5. r2 is an object of Rectangle
print(r1 is r2) #state the address of r1 is the same of r2, false in this case
print(r1 == r2) #state the value of r1 is the same of r2, 10=10, 20=20,  true in this case
print(r1 == 100) #state the type of r1 is the same of 100, false is this case
print(r1.width)
print(r1.color, r2.color)
print(r1.area())
print(r1 < r2)
print(str(r1))  #result shows: <__main__.Rectangel object at 0x7ba42a620c10>, it is an address. main is taken from 
#the file name:mmain.py. but when __str__ is redefined in line15, str follows line15 and run the function here
#print(r1.to_string())
#__xx__ is an internal function
#__str__ is the string representation of the object. Here the object is r1.
print(Rectangle.__str__(r1)) #   def __str__(self): # write a __str__ to replace the __str__ inside python
print(r1.__repr__) #show the results <bound method Rectangle.__repr__ of Rectangel (10, 20)>
print(dir(r1))