On Mon, 05 Sep 2005 14:26:14 -0400, Terry Reedy wrote: > > "Stephan Diehl" <[EMAIL PROTECTED]> wrote in message > news:[EMAIL PROTECTED] >>I just found out by accident, that slice indices can be larger than >> the length of the object. For example >>>>> 'test'[:50] >> 'test' [...] >> Does anybody know, why this is preferred to just raising an error? > > Slicing was intentially designed to always give an answer (given int > coords) and never say 'can't answer' (whether by exception or a None > return). This avoids having to call len() when you don't care and avoids > having to use try:...except:... or conditionalize the code when it is not > needed. For instance c=s[0:1] is equivalent to > > c=s[0:min(1,len(s))] # if slice had to be exact, or > > c = s and s[0] or '' # or > > if s: > c = s[0] > else: > c = '' # or > > try: > c = s[0] > except IndexError: > c = '' > > People occasionally post buggy code which simply needs s[0] changed to > s[0:1]. > > The form s[i:], which I am sure you agree is useful, is effectively > equivalent to eithers[i:len(s)] or s[i:<maxint>]. The latter view > generalizes to iterables without a knowable length.
I do think that this is useful and can save some lines of code. Just never expected this. > > Terry J. Reedy -- http://mail.python.org/mailman/listinfo/python-list
