Angelo Secchi wrote:

Hi, I have the following script

import fileinput import string from math import * from scipy import * from rpy import * import Numeric import shelve import sys

def dpolya1(n,N,b,a): a=float(a) b=float(b) L=784 probs=((special.gammaln(N+1)+special.gammaln(L*(a/b))+special.gammaln((a/b)+n)+special.gammaln((a/b)*(L-1)+N-n))-(special.gammaln(L*(a/b)+N)+special.gammaln(a/b)+special.gammaln(n+1)+special.gammaln(N-n+1)+special.gammaln(L*(a/b)-(a/b))))#) return probs

and I observe the following "strange" (for me of course) behaviour

...

...

...

dpolya1(1,2,0.5,0.4)

-5.9741312822170585

...

...

...

type(dpolya1(1,2,0.5,0.4))

<type 'float64scalar'>

...

...

...

exp(dpolya1(1,2,0.5,0.4))

Traceback (most recent call last): File "<stdin>", line 1, in ? AttributeError: 'numpy.ndarray' object has no attribute 'exp'

I do not understand what's wrong. Any help?

Probably rpy (which still uses Numeric, right?) is exposing Numeric's exp() implementation and overriding the one that you got from scipy (which is numpy's, I presume). When Numeric's exp() is confronted with an object that it doesn't recognize, it looks for a .exp() method to call.

If you want to avoid this situation in the future, don't use the "from foo import *" form. It makes debugging problems like this difficult.