On Oct 24, 4:05 pm, Lou Pecora <[EMAIL PROTECTED]> wrote: > 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
Simple minded indeed. >>> factorial(3) 0.0 > > 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- Hide quoted text - > > - Show quoted text - -- http://mail.python.org/mailman/listinfo/python-list
