# Identifying the start of good data in a list

Matthew Fitzgibbons elessar at nienna.org
Wed Aug 27 01:01:04 CEST 2008

```tkpmep at hotmail.com wrote:
> I have a list that starts with zeros, has sporadic data, and then has
> good data. I define the point at  which the data turns good to be the
> first index with a non-zero entry that is followed by at least 4
> consecutive non-zero data items (i.e. a week's worth of non-zero
> data). For example, if my list is [0, 0, 1, 0, 1, 2, 3, 4, 5, 6, 7, 8,
> 9], I would define the point at which data turns good to be 4 (1
> followed by 2, 3, 4, 5).
>
> I have a simple algorithm to identify this changepoint, but it looks
> crude: is there a cleaner, more elegant way to do this?
>
>     flag = True
>     i=-1
>     j=0
>     while flag and i < len(retHist)-1:
>         i += 1
>         if retHist[i] == 0:
>             j = 0
>         else:
>             j += 1
>             if j == 5:
>                 flag = False
>
>     del retHist[:i-4]
>
>
> Thomas Philips
> --
> http://mail.python.org/mailman/listinfo/python-list
>

Maybe this will do?

reHist = [0, 0, 1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
count = 0
for i, d in enumerate(reHist):
if d == 0:
count = 0
else:
count += 1
if count == 5:
break
else:
raise Exception("No data found")
reHist = reHist[i-4:]
print reHist

-Matt

```