On 3月29日, 下午8时22分, Michael Bentley <[EMAIL PROTECTED]> wrote: > 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
oh yes, it's the "break" I forgot... Thank you, it helps me a lot!
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