I'm trying to make a constructor without hardcoding all of the values

[RedSkeleton007]

I'm new to Python Classes. I'm trying to tell the constructor to associate a size with a price, but it's not liking it.

Here is the module code (PublicPizzaClass.py) with the class constructor in it:

#!/usr/bin/env python3
#PublicPizzaClass.py

class Pizza:
    #a constructor that initializes 3 attributes for any-topping pizzas.
    #right now, the attributes are public, so code outside of this class
    #will be able to get and set the values of these attributes.
    def __init__(pizza, name, size, price, taxPercent):
        pizza.name = name
        pizza.size = size #small = $7, medium = $9, large = $10
        pizza.price = getSizePrice()

    #a method that associates a size with a price
    def getSizePrice(pizza):
        if pizza.size == "Small":
            pizza.price = 7.00
        elif pizza.size == "Medium":
            pizza.price = 9.00
        elif pizza.size == "Large":
            pizza.price = 10.00
        return pizza.price

    #a method that uses two attributes to perform a calculation
    def getTaxAmount(pizza):
        pizza.price = getSizePrice()
        return pizza.price * 0.05

    #a method that calls another method to perform a calculation
    def getTotalPrice(pizza):
        return pizza.price + getTaxAmount()

And here is the code (PublicPizzaClassUser.py) that I'm trying to get to use the module's code:

#!/usr/bin/env python3
#PublicPizzaClassUser.py

#import the class from the PublicPizzaClass module
from PublicPizzaClass import Pizza

#create two pizza objects
pizza1 = Pizza("Pepperoni", "Large", getSizePrice())
pizza2 = Pizza("Sausage", "Medium", getSizePrice())

print("Name:            {:s}".format(pizza1.name))
print("Price:           {:.2f}".format(pizza1.getSizePrice()))
print("Tax Amount:      {:.2f}".format(pizza1.getTaxAmount()))
print("Total Price:     {:.2f}".format(pizza1.getTotalPrice()))

The error is:

Error:
==== RESTART: I:/Python/Python36-32/SamsPrograms/PublicPizzaClassUser.py ====
Traceback (most recent call last):
  File "I:/Python/Python36-32/SamsPrograms/PublicPizzaClassUser.py", line 8, in <module>
    pizza1 = Pizza("Pepperoni", "Large", getSizePrice())
NameError: name 'getSizePrice' is not defined

It's starting to look like using function calls to define constructor attributes is a no-no. Is that correct?

[ajaykumar]

I also tried this code. it seems there is no error but unfortunately don't work.

[Gribouillis]

Here is a working version

#!/usr/bin/env python3
#PublicPizzaClass.py
 
class Pizza:
    #a constructor that initializes 3 attributes for any-topping selfs.
    #right now, the attributes are public, so code outside of this class
    #will be able to get and set the values of these attributes.
    def __init__(self, name, size, price=None, taxPercent=0.05):
        self.name = name
        self.size = size #small = $7, medium = $9, large = $10
        self.taxPercent = taxPercent
        self.price = self.getSizePrice(size) if price is None else price
        
    #a method that associates a size with a price
    @staticmethod
    def getSizePrice(size):
        if size == "Small":
            price = 7.00
        elif size == "Medium":
            price = 9.00
        elif size == "Large":
            price = 10.00
        return price
 
    #a method that uses two attributes to perform a calculation
    def getTaxAmount(self):
        return self.price * self.taxPercent
 
    #a method that calls another method to perform a calculation
    def getTotalPrice(self):
        return self.price + self.getTaxAmount()
    
 
#create two pizza objects
pizza1 = Pizza("Pepperoni", "Large")
pizza2 = Pizza("Sausage", "Medium")
 
print("Name:            {:s}".format(pizza1.name))
print("Price:           {:.2f}".format(pizza1.price))
print("Tax Amount:      {:.2f}".format(pizza1.getTaxAmount()))
print("Total Price:     {:.2f}".format(pizza1.getTotalPrice()))

Note that the implicit first argument in methods is usually named 'self' instead of 'pizza'. In this version, the constructor gives you the opportunity to give a price and tax percent, but if you don't give it, it chooses the default (price from size and tax 0.05).

[RedSkeleton007]

Next problem. My book has showed the different options for constructors, and how to use values of an object created with those constructors. I understand how to create a function that does things with the values from an object instance, but I'm not sure what to make of this:

def methodName(self[, parameters]):
    statements

The square brackets look really weird. In my attempt to try to create my own example, this is what I came up with:

#!/usr/bin/env python3
#PublicPizzaClass.py

##class Pizza:
##    #a constructor that initializes 4 attributes for any-topping pizzas.
##    #right now, the attributes are public, so code outside of this class
##    #will be able to get and set the values of these attributes.
##    def __init__(pizza, name, size, price):
##        pizza.name = name
##        pizza.size = size #small = $7, medium = $9, large = $10
##        pizza.price = price

def Pizza(pizza[, name, size, price]):
    pizza.name = name
    pizza.size = size
    pizza.price = price

    #a method that uses two attributes to perform a calculation
    def getTaxAmount(pizza):
        return pizza.price * 0.05

    #a method that calls another method to perform a calculation
    def getTotalPrice(pizza):
        return pizza.price + pizza.getTaxAmount()

After running this python file:

#!/usr/bin/env python3
#PublicPizzaClassUser.py

#import the class from the PublicPizzaClass module
from PublicPizzaClass import Pizza

#create two pizza objects
pizza1 = Pizza("Pepperoni", "Large", 10.00)
pizza2 = Pizza("Sausage", "Medium", 9.00)

myPizza = pizza1.name
print(myPizza)#should print "Pepperoni"

The error I got was:

Error:
==== RESTART: I:/Python/Python36-32/SamsPrograms/PublicPizzaClassUser.py ====
Traceback (most recent call last):
  File "I:/Python/Python36-32/SamsPrograms/PublicPizzaClassUser.py", line 5, in <module>
    from PublicPizzaClass import Pizza
  File "I:/Python/Python36-32/SamsPrograms\PublicPizzaClass.py", line 13
    def Pizza(pizza[, name, size, price]):
                   ^
SyntaxError: invalid syntax

Seriously, what is up with the method that encloses its parameters in square brackets? If that type of method isn't supposed to act as a constructor, what is it for?

[ajaykumar]

Thanks for considering me you have made this very good !
but it doesn't take any argument as a input

[RedSkeleton007]

Here is a working version

        self.price = self.getSizePrice(size) if price is None else price

Note that the implicit first argument in methods is usually named 'self' instead of 'pizza'. In this version, the constructor gives you the opportunity to give a price and tax percent, but if you don't give it, it chooses the default (price from size and tax 0.05).

I don't see anything like

price = input("Specify a price: ")

in there, so what part of that line of your code above allows the user to choose a price?

[Gribouillis]

what part of that line of your code above allows the user to choose a price?

The code that uses the class can choose the price. One can write

pizza1 = Pizza("Pepperoni", "Large")
pizza1 = Pizza("Pepperoni", "Large", 12.0)
pizza1 = Pizza("Pepperoni", "Large", price=12.0)
pizza1 = Pizza("Pepperoni", "Large", taxPercent=0.07)
pizza1 = Pizza("Pepperoni", "Large", price=11.0, taxPercent=0.06)

---

what is up with the method that encloses its parameters in square brackets?

This syntax is only used in the documentation to indicate optional arguments. It is not valid syntax in real code.

[buran]

class Pizza():
    def __init__(self, name, size):
        self.name = name.capitalize()
        self.size = size.lower()
    
    @property
    def price(self):
        prices = {'Margherita':{'small':7.00, 'medium':9.00, 'large':11.00},
                  'Pepperoni':{'small':8.00, 'medium':10.00, 'large':12.00}}
        return prices[self.name][self.size]
        
    def __str__(self):
        return ('{} {}'.format(self.size, self.name))
                  
small_margherita = Pizza('Margherita', 'small')
large_pepperoni = Pizza('pepperoni', 'large')

print('{}, price: {:.2f}'.format(small_margherita, small_margherita.price))
print('{}, price: {:.2f}'.format(large_pepperoni, large_pepperoni.price))

Output:
small Margherita, price: 7.00
large Pepperoni, price: 12.00