# [Tutor] list comprehension problem

bob gailer bgailer at gmail.com
Sat Jul 4 02:56:21 CEST 2009

```Dinesh B Vadhia wrote:
> I'm suffering from brain failure (or most likely just being brain
> less!) and need help to create a list comprehension for this problem:
>
> d is a list of integers: d = [0, 8, 4, 4, 4, 7, 2, 5, 1, 1, 5, 11, 11,
> 1, 6, 3, 5, 6, 11, 1]
>
> Want to create a new list that adds the current number and the prior
> number, where the prior number is the accumulation of the previous
> numbers ie.
>
> dd = [0, 8, 12, 16, 20, 27, 29, 34, 35, 36, 41, 52, 63, 64, 70, 73,
> 78, 84, 95, 96]
>
> A brute force solution which works is:
>
> >>> dd = []
> >>> y = d[0]
> >>> for i, x in enumerate(d):
> >>>        y += x
> >>>        dd.append(y)
>
> Is there a list comprehension solution?

Python has a reduce function that applies an operator (such as +) to
successive elements of an iterable giving a single value (in your case
that is 96).

APL has both reduce and scan, where scan gives you exactly what you