I could not resist to propose an other solution: r = array([0,2,5,6,8]) l = (r[:,NewAxis] + r[NewAxis,:]).flat -----Original Message----- From: Hee-Seng Kye [mailto:kyeser@earthlink.net] Sent: mercredi 14 juillet 2004 4:22 To: numpy-discussion@lists.sourceforge.net Subject: [Numpy-discussion] a 'for' loop within another 'for' loop? Hi. I wrote a program to calculate sums of every possible combinations of two indices of a list. The main body of the program looks something like this: r = [0,2,5,6,8] l = [] for x in range(0, len(r)): for y in range(0, len(r)): k = r[x]+r[y] l.append(k) print l 1. I've heard that it's not a good idea to have a 'for' loop within another 'for' loop, and I was wondering if there is a more efficient way to do this. 2. Does anyone know if there is a built-in function or module that would do the above task in NumPy or Numarray (or even in Python)? I would really appreciate it if anyone could let me know. Thanks for your help!