passing values between methods, Python OOP, Method not getting-CodePudding

I am learning about classes and methods, trying to modify a simple python code so I can pass an attribute value using a method. I could pass the attribute for the setyear() method. However, I am unable to use it and perform a simple mathematical operation (e.g, age calculation) as in the agecalc() method. Wonder if you can please point out why am I getting 0 instead of 10?

class Dog:
    def __init__(self, name, born, breed):
        self.name = name
        self.born = born     # year born
        self.breed = breed
        self.year = 0
        self.age=0
  
    
    def setyear(self, year):
        #self.year = year-self.born     
        self.year = year
    
    def agecalc(self, year):
        self.age = self.year - self.born  ##*** keeps giving me 0??
        

mydog1 = Dog (name = "Lassy", born = 2015, breed = "Husky") 

mydog1.setyear(2025) # setting the year we wish to calculate the dog's age at
   

# The following is sub ideal. 
print ("dog age =", mydog1.year - mydog1.born)  
# looking replace the above line with the agecalc method i.e. print (agecalcl(2025))


# Tried the following one as well and it keeps giving me `None`
print (mydog1.agecalc(2025))

CodePudding user response：

You didn't return the age; you only set an attribute.

mydog1.agecalc(2025)
print(mydog1.age)

Alternatively, you can have agecalc return the age instead of storing the age. The current year isn't really a property of the dog like its birth year is.

class Dog:
    def __init__(self, name, born, breed):
        self.name = name
        self.born = born     # year born
        self.breed = breed
  
    
    def agecalc(self, year):
        return year - self.born
        

mydog1 = Dog(name="Lassy", born=2015, breed="Husky") 
print("My dog is", mydog1.agecalc(2025), "years old.")

CodePudding user response：

your function should be this:

def agecalc(self, year):
    self.age = year - self.born
    return self.age

you mixed up year (the year you pass in as an argument) with self.year

also, you print, so I guess you want to return the value or access the age directly (not so OOP'ish, but python allows it)

mydog1.agecalc(2025)
print(mydog1.age)

CodePudding user response：

you are missing the return statement try:

def agecalc(self, year):
    self.age = year - self.born
    return self.age