classes.py

# Classes — basic OOP in Python.
#
# Demonstrates __init__, instance methods, __str__, and __eq__.
#
# The Line class represents a line segment between two points.
# - __init__  : initialises the object's attributes
# - length()  : computes the Euclidean distance between the two points
# - __str__   : controls how the object is printed
# - __eq__    : controls how two objects are compared with ==

from math import sqrt


class Line:
    def __init__(self, x1, y1, x2, y2):
        self.x1 = x1
        self.y1 = y1
        self.x2 = x2
        self.y2 = y2

    def length(self):
        return sqrt((self.x2 - self.x1) ** 2 + (self.y2 - self.y1) ** 2)

    def __str__(self):
        return f'Line({self.x1}, {self.y1}) -> ({self.x2}, {self.y2})'

    def __eq__(self, other):
        if isinstance(other, Line):
            return (self.x1 == other.x1 and self.y1 == other.y1 and
                    self.x2 == other.x2 and self.y2 == other.y2)
        return False


line1 = Line(0, 0, 10, 10)
line2 = Line(0, 0, 20, 10)
line3 = Line(0, 0, 10, 10)

print(line1)
print(f'Length: {line1.length():.4f}')

print(line1 == line2)    # False
print(line1 == line3)    # True