In article <[EMAIL PROTECTED]>, Nick Craig-Wood <[EMAIL PROTECTED]> wrote:
> Py-Fun <[EMAIL PROTECTED]> wrote: > > I'm stuck trying to write a function that generates a factorial of a > > number using iteration and not recursion. Any simple ideas would be > > appreciated. > > Here is the math geek answer ;-) > > import math > > def factorial(i): > n = i + 1 > return math.exp(-n)*(n**(n-0.5))*math.sqrt(2*math.pi)*(1. + 1./12/n + > 1./288/n**2 - 139./51840/n**3) > > Works for non integer factorials also... > > See here for background > > http://mathworld.wolfram.com/StirlingsSeries.html Well, that's Sterling's formula. You do have to worry about convergence/accuracy. How about (for intergers - simple-minded version): def factorial(i): fact=1.0 for n in xrange(i): fact=n*fact return fact There might even be an array method that can be adapted to get the product. Is there a product method? (analogous to a sum method) Then you could use, arr=arange(i)+1 fact=arr.product() # or something like that -- -- Lou Pecora -- http://mail.python.org/mailman/listinfo/python-list
