OOP Python add some attribute to the base class?

Question

I am learning OOP with python .trying with small console application Stock

class Stock(object):

    def __init__(self, stockName, stockLimit, inStock, rentPrice):

        self.stockName  = stockName   # private
        self.stockLimit = stockLimit  # private
        self.inStock    = inStock     # private
        self.rentPrice  = rentPrice   # private

    def inputStock(self, nProduct):

        if(nProduct >= (self.stockLimit - self.inStock)):
            self.inStock = self.stockLimit
        else:
            self.inStock += nProduct 

    def invoice(self, nDay):
        return self.rentPrice * nDay


class StockProduct(Stock):

    def __init__(self, factor):
        # the base-class constructor:
        Stock.__init__(self, stockName, stockLimit, inStock, rentPrice)
        self.factor = factor # Extra for this stock

    def invoice(self, nDay):
        return Stock.invoice(self, nDay) * self.factor

class StockMaterial(Stock):

    def __init__(self,factor):
        # the base-class constructor:
        Stock.__init__(self, stockName, stockLimit, inStock, rentPrice)
        self.factor = factor # Extra for this stock

    def invoice(self,nDay):
        return Stock.invoice(self, nDay)*self.factor

if __name__ == "__main__":

    N = nDay = 0
    myStock = Stock("stock111", 500, 200, 400000)
    N = float(raw_input("How many product into stock: "+str(myStock.stockName)+" ? "))
    myStock.inputStock(N)
    nDay = int(raw_input("How many days for rent : "+str(myStock.stockName)+" ? "))
    print "Invoice for rent the stock: "+str(myStock.stockName)+ " = "+ str(myStock.invoice(nDay))

    StockProduct = StockProduct("stock222",800, 250, 450000, 0.9)

    N = float(raw_input("How many product into stock: "+str(StockProduct.stockName)+" ? "))
    StockProduct.inputStock(N)
    nDay = int(raw_input("How many days for rent : "+str(StockProduct.stockName)+" ? "))
    print "Invoice for rent the stock: "+str(StockProduct.stockName)+ " = "+ str(StockProduct.invoice(nDay))

I have two questions:

with my method invoice, how Can I do method overloading in python ?

I added some attribute in the child I got the following error message:

StockProduct = StockProduct("stock222",800, 250, 450000, 0.9)
TypeError

error: __init__() takes exactly 2 arguments (6 given)

What I should do here?

Anybody can help me please?

Thank in advance

highBandWidth · Accepted Answer · 2011-04-16 16:31:22Z

6

The overloaded invoice in the derived class should work fine.

Your base class constructor needs to have all the parameters, so :

class StockProduct(Stock):
    def __init__(self, stockName, stockLimit, inStock, rentPrice, factor):
        # the base-class constructor:
        Stock.__init__(self, stockName, stockLimit, inStock, rentPrice)
        self.factor = factor

    def invoice(self, nDay):
        return Stock.invoice(self, nDay) * self.factor

edited Apr 16, 2011 at 16:31

answered Apr 15, 2011 at 20:26

highBandWidth

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Comments

sverre · Accepted Answer · 2011-04-15 20:23:21Z

2

1 - Yes, you can do method overloading in python.

2 - Your child class changed the method signature. You should declare it as

def __init__(self, stockName, stockLimit, inStock, rentPrice, factor):

if you want to construct it with all the arguments from the parent class plus some extra.

answered Apr 15, 2011 at 20:23

sverre

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