basic_class_example.py

# A class is a cookie cutter that can be used to stamp out instances
# This class models a farm (well one with animals on it, at least)
# This class inherits from "object"
class Farm(object):
    
    def __init__(self, length, width, sheep, cattle, pigs, poultry):
        self.length = length
        self.width = width
        self.sheep = sheep
        self.cattle = cattle
        self.pigs = pigs
        self.poultry = poultry

    # define an instance method
    def sell_all_sheep(self):
        self.sheep = 0
    
    # define a second instance method
    def buy_sheep(self):
        self.sheep += 5
    
    # assumes a rectangular farm
    # this method is disguised to look like a property
    @property
    def area(self):
        return self.width * self.length
    
    @property
    def total_livestock(self):
        return self.sheep + self.cattle + self.pigs + self.poultry
    


# Create an instance of Farm
myfarm = Farm(10, 20, 4, 5, 6, 7)

# access a property
print("Number of sheep:", myfarm.sheep)

# call a method
myfarm.sell_all_sheep()

print("Number of sheep after sale:", myfarm.sheep)

# get the area of the farm - note property syntax
print("Area of the farm:", myfarm.area, "units")

# get the total livestock - note property syntax
print("Total livestock:", myfarm.total_livestock)

# call a method
myfarm.buy_sheep()

print("Number of sheep after buying some:", myfarm.sheep)

# alternative syntax, passing in instance
Farm.sell_all_sheep(myfarm)

print("Number of sheep after another sale:", myfarm.sheep)