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Sign up| PEP: 260 | |
| Title: Simplify xrange() | |
| Version: $Revision$ | |
| Last-Modified: $Date$ | |
| Author: guido@python.org (Guido van Rossum) | |
| Status: Final | |
| Type: Standards Track | |
| Content-Type: text/x-rst | |
| Created: 26-Jun-2001 | |
| Python-Version: 2.2 | |
| 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: |