Significance of "start" parameter to string method "endswith"

[John Machin]

On Apr 20, 6:36 am, subscriber123 <collinsto... at gmail.com> wrote:
> On Apr 19, 3:58 pm, Boris Dušek <boris.du... at gmail.com> wrote:
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> > Hello,
>
> > what is the use-case of parameter "start" in string's "endswith"
> > method? Consider the following minimal example:
>
> > a = "testing"
> > suffix="ing"
> > a.endswith(suffix, 2)
>
> > Significance of "end" is obvious. But not so for "start".
>
> > Let's assume the "end" parameter is not used - then the function
> > should simple check that the last "len(suffix)" characters of "a" are
> > equal to "ing", no matter where we start (the function does not *scan*
> > the string from the "start", does it?)
> > Only case where it would make difference is if we had start +
> > len(suffix) < len(a)     (excuse possible "of-by-one" error :-)
> > Then the function would never return True. But is there a real use
> > case when we would test for endswith like this? (knowing that it must
> > return false?)
>
> > Thanks for any ideas/experience.
> > Boris
>
> Basically, this must be so in order for this to be Pythonic. This is
> because it is an object oriented language, and functions can be passed
> as arguments. Say, for example, you have the following function:
>
> def foo(function,instance,param):
>     if function(instance,param,2,4):
>         return True
>     else: return False

Perhaps
    return function(instance, param, 2, 4)
would have a higher pythonicity index :-)

>
> The function must work whether you pass it
> foo(str.endswith,"blaahh","ahh"), or
> foo(str.startswith,"blaahh","aah"). This is a really bad example, but
> it gets the point across that similar functions must have similar
> parameters in order to be Pythonic.
>
> I personally have never used the second or third parameters in this
> function nor in str.startswith.