On Mar 29, 2007, at 6:51 AM, Su Y wrote:
>
> I want find the first number in extend[] which is larger than num, so
> I wrote:
> def find(num):
> count=0
> for elem in extend:
> if elem<num:
> count+=1
> return count
>
> I found that if extend[] is monotonous, like [1.1, 2.3, 3.2, 4.5,
> 5.6],
> it works fine: find(4) returns 3, extend[3] is 4.5.
> But, if extend[] is not monotonous, like [1.1, 2.3, 3.2, 4.5, 5.6,
> 4.6, 3.4, 2.1, 0.3],
> find(4) returns 6, extend[6] is 3.4!
>
> what's going on here? I really can't understand....
find() loops through the list, and every time it finds a value less
than num it increments count. So in your second example the values
1.1, 2.3, 3.2, 3.4, 2.1, and 0.3 are all less than 4, which means
count will be 6.
As you learned, a sorted list behaves as you expect. So one approach
is to sort your list first. But another perhaps better approach is
to do something like:
def find(num):
# check to make sure there *is* a value greater than num
if max(extend) > num:
# then return the smallest value that is greater than num
return min([x for x in extend if x > num])
else:
return None
Hope this helps,
Michael
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