85 lines
2.2 KiB
Plaintext
85 lines
2.2 KiB
Plaintext
PEP: 260
|
||
Title: Simplify xrange()
|
||
Version: $Revision$
|
||
Author: guido@python.org (Guido van Rossum)
|
||
Status: Draft
|
||
Type: Standards Track
|
||
Python-Version: 2.2
|
||
Created: 26-Jun-2001
|
||
Post-History: 26-Jun-2001
|
||
|
||
Abstract
|
||
|
||
This PEP proposes to strip the xrange() object from some rarely
|
||
used behavior like x[i:j] and x*n.
|
||
|
||
|
||
Problem
|
||
|
||
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.
|
||
|
||
|
||
Proposed Solution
|
||
|
||
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[i:j] (slicing)
|
||
x*n, n*x (sequence-repeat)
|
||
cmp(x1, x2) (comparisons)
|
||
i in x (containment test)
|
||
x.tolist() method
|
||
x.start, x.stop, x.step attributes
|
||
|
||
I also propose to change the signature of the PyRange_New() C API
|
||
to remove the 4th argument (the repetition count).
|
||
|
||
By implementing a custom iterator type, we could speed up the
|
||
common use, but this is optional (the default sequence iterator
|
||
does just fine).
|
||
|
||
|
||
Scope
|
||
|
||
This PEP affects the xrange() built-in function and the
|
||
PyRange_New() C API.
|
||
|
||
|
||
Risks
|
||
|
||
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.
|
||
|
||
|
||
Transition
|
||
|
||
For backwards compatibility, the existing functionality will still
|
||
be present in Python 2.2, but will trigger a warning. A year
|
||
after Python 2.2 final is released (probably in 2.4) the
|
||
functionality will be ripped out.
|
||
|
||
|
||
Copyright
|
||
|
||
This document has been placed in the public domain.
|
||
|
||
|
||
Local Variables:
|
||
mode: indented-text
|
||
indent-tabs-mode: nil
|
||
End:
|