Whither binary search?

[John Machin]

Fredrik Lundh wrote:
> Neil Cerutti wrote:
>
> >> bisect...
> >
> > That doesn't tell me if an item doesn't exist in the sequence
> > though, does it?  Maybe I'm being dense.
>
> I guess you could use something like
>
> import bisect
>
> def check(list, item):
>      try:
> 	return list[bisect.bisect_left(list, item)] == item
>      except IndexError:
> 	return False
>
> but unless your lists are really large, or your objects are expensive to
> compare, you could probably just use "in" instead.
>
>  > My guess nobody keeps their sequences sorted in Python.
>
> well, people tend to use dictionaries when they need to look things up
> quickly...

... like those paper dictionaries with the words in alphabetical order
:-)

A common use case for looking things up in a sorted list is an
in-memory table of dates and rates (interest rates, insurance premium
rates, fee rates). In a big batch job, this sure beats doing "select
rate from table where ? between low_date and high_date" each time you
need a rate.

Cheers,
John