[Python-Dev] PEP 260: simplify xrange()
Guido van Rossum
Tue, 26 Jun 2001 13:59:55 -0400
Here's another sweet and short PEP. What do folks think? Is
xrange()'s complexity really worth having?
--Guido van Rossum (home page: http://www.python.org/~guido/)
Title: Simplify xrange()
Version: $Revision: 1.1 $
Author: email@example.com (Guido van Rossum)
Type: Standards Track
This PEP proposes to strip the xrange() object from some rarely
used behavior like x[i:j] and x*n.
The xrange() function has one idiomatic use:
for i in xrange(...): ...
However, the xrange() object has a bunch of rarely used behaviors
that attempt to make it more sequence-like. These are so rarely
used that historically they have has serious bugs (e.g. off-by-one
errors) that went undetected for several releases.
I claim that it's better to drop these unused features. This will
simplify the implementation, testing, and documentation, and
reduce maintenance and code size.
I propose to strip the xrange() object to the bare minimum. The
only retained sequence behaviors are x[i], len(x), and repr(x).
In particular, these behaviors will be dropped:
x*n, n*x (sequence-repeat)
cmp(x1, x2) (comparisons)
i in x (containment test)
x.start, x.stop, x.step attributes
By implementing a custom iterator type, we could speed up the
common use, but this is optional (the default sequence iterator
does just fine).
I expect it will take at most an hour to rip it all out; another
hour to reduce the test suite and documentation.
This PEP only affects the xrange() built-in function.
Somebody's code could be relying on the extended code, and this
code would break. However, given that historically bugs in the
extended code have gone undetected for so long, it's unlikely that
much code is affected.
This document has been placed in the public domain.