# Array of 2^n

Chris Barker chrishbarker at home.net
Mon Oct 22 19:48:56 CEST 2001

```Moshe wrote:
>
> Okay, python newbie here. I'm liking what I see, but it seems like there
> are holes in the features of python's objects. I remember programming in
> squeak (an extension of smalltalk), and you could do complex operations on
> lists, and it would apply the result to each item. I want to make a n-item
> list such that mylist[i] = 2**i. How can I generate such a list in Python?

IF you really want a list, you have been given a number of options. If,
however, you are doing this a lot, with large sequences of numbers, you
are probably doing other math operations as well, and you want a nice
fast way to do operations on sequences of numbers that has a clean
sequence. For this you want the Numeric module:

http://sourceforge.net/projects/numpy

Then you can do:

from Numeric import *

myArray = 2**arange(i)

You can also do all kinds fo nifty element-wise math with all the basic
operators and math functions. Here is a quick example for the root mean
square values of a rank-1 array:

sqrt(sum(array**2)/(len(myArray))

Numeric has many other nifty features as well. If you are working with
numbers, it is a wonderful tool.

-Chris

--
Christopher Barker,
Ph.D.
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```