help with object method calls

[kdt]

Hi,

Been reading about objects today. I have a program, that I am trying to rewrite as much as possible as objects. I want to write the following two functions as methods in the Number class:

def factorial(n):
    '''
    n is a positive integer;
    RETURNS: integer factorial of n from a recursive function.
    '''
    f = 1
    while (n > 0):
        f = f * n
        n = n - 1
    return f
 
def binomial(n, p, x):
    '''
    n is a positive integer number of independent Bernoulli Trials;
        p is the probability of success of the binomial event;
        x is the positive integer number of Bernoulli Trials of n.
    RETURNS: The probability of success from a series of Bernoulli Trials
    '''
    fn = factorial(n)
    return (fn/(factorial(x)*(factorial(n-x))))*(p**x)*((1-p)**(n-x))
 
 

I am stuck on the last line of the binomial, as I seem to have to instantiate x and n-x as Numbers. Is this right? Or is it better to not make objects out of them? Thanks

 
class Numbers():
    def __init__(self, numbers):
        self.numbers = numbers
 
    def factorial(self):
        f=1
        while (self.numbers>0):
            f*=self.numbers
            self.numbers-=1
        return f
 
    def binomial(self, x, p):
        fn=self.factorial()
        y=Numbers(x)
        return (fn/(y.factorial()* (y-1).factorial))# stuck here
 
 

[bvdet]

Hi,

Been reading about objects today. I have a program, that I am trying to rewrite as much as possible as objects. I want to write the following two functions as methods in the Number class:

def factorial(n):
    '''
    n is a positive integer;
    RETURNS: integer factorial of n from a recursive function.
    '''
    f = 1
    while (n > 0):
        f = f * n
        n = n - 1
    return f
 
def binomial(n, p, x):
    '''
    n is a positive integer number of independent Bernoulli Trials;
        p is the probability of success of the binomial event;
        x is the positive integer number of Bernoulli Trials of n.
    RETURNS: The probability of success from a series of Bernoulli Trials
    '''
    fn = factorial(n)
    return (fn/(factorial(x)*(factorial(n-x))))*(p**x)*((1-p)**(n-x))
 
 

I am stuck on the last line of the binomial, as I seem to have to instantiate x and n-x as Numbers. Is this right? Or is it better to not make objects out of them? Thanks

 
class Numbers():
    def __init__(self, numbers):
        self.numbers = numbers
 
    def factorial(self):
        f=1
        while (self.numbers>0):
            f*=self.numbers
            self.numbers-=1
        return f
 
    def binomial(self, x, p):
        fn=self.factorial()
        y=Numbers(x)
        return (fn/(y.factorial()* (y-1).factorial))# stuck here
 
 

This seems to work. You may need to do some error trapping.

class Numbers(object):
    def __init__(self, numbers):
        self.numbers = numbers
 
    def factorial(self, x):
        f=1
        while (x>0):
            f*=x
            x-=1
        return f
 
    def binomial(self, x, p):
        fn=self.factorial(self.numbers)
        return (float(fn)/(self.factorial(x)*\
                    (self.factorial(self.numbers-x)-1))
                )*(p**x)*((1-p)**(self.numbers-x)

[kdt]

This seems to work. You may need to do some error trapping.

class Numbers(object):
    def __init__(self, numbers):
        self.numbers = numbers
 
    def factorial(self, x):
        f=1
        while (x>0):
            f*=x
            x-=1
        return f
 
    def binomial(self, x, p):
        fn=self.factorial(self.numbers)
        return (float(fn)/(self.factorial(x)*\
                    (self.factorial(self.numbers-x)-1))
                )*(p**x)*((1-p)**(self.numbers-x)

Thanks bvdet, was struggling with this yesterday. There's an extra '-1' in your code, but apart from that, it works fine. The only obscurity is having to pass two parameters for the factorial method - although I understand that this is required for it to be able to be called from the binomail method. Is it better practice to keep it like this, or should it be left in functions? Just looking for an opinion here, still a newb so want to learn the best practices. Cheers

class Number(object):
    def __init__(self, number):
        self.number = number
 
    def factorial(self, x):
        f=1
        while (x>0):
            f*=x
            x-=1
        return f
 
    def binomial(self, x, p):
        fn=float(self.factorial(self.number))
        return (fn/(self.factorial(x)*\
                           (self.factorial(self.number-x))))*\
                           (p**x)*((1-p)**(self.number-x))
    def __str__(self):
        return str(self.number)
 
 
n = Number(10)
print n.factorial(6)
print n.binomial(3, 0.8)
 
>>> 
720
0.000786432