New submission from Manuel de la Pena <[email protected]>:
The problem is simple, the code that allows to use binary strings and unicode
is making more calls that needed to isinstance(path, bytes) since the result of
the code is not shared. For example, the following calls are present in the
module:
def _get_empty(path):
if isinstance(path, bytes):
return b''
else:
return ''
def _get_sep(path):
if isinstance(path, bytes):
return b'\\'
else:
return '\\'
def _get_altsep(path):
if isinstance(path, bytes):
return b'/'
else:
return '/'
def _get_bothseps(path):
if isinstance(path, bytes):
return b'\\/'
else:
return '\\/'
def _get_dot(path):
if isinstance(path, bytes):
return b'.'
else:
return '.'
...
And then something similar to the following is found in the code:
def normpath(path):
"""Normalize path, eliminating double slashes, etc."""
sep = _get_sep(path)
dotdot = _get_dot(path) * 2
special_prefixes = _get_special(path)
if path.startswith(special_prefixes):
# in the case of paths with these prefixes:
# \\.\ -> device names
# \\?\ -> literal paths
# do not do any normalization, but return the path unchanged
return path
path = path.replace(_get_altsep(path), sep)
prefix, path = splitdrive(path)
As you can see the isinstance call is performed more than needed which
certainly affects the performance of the path operations.
The attached patch removes the number of calls to isinstance(obj, bytes) and
also ensures that the function that returns the correct literal is as fast as
possible by using a dict.
----------
components: Windows
files: less_isinstance.patch
hgrepos: 140
keywords: patch
messages: 164842
nosy: mandel
priority: normal
severity: normal
status: open
title: isinstance is called a more times that needed in ntpath
versions: Python 3.3
Added file: http://bugs.python.org/file26294/less_isinstance.patch
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Python tracker <[email protected]>
<http://bugs.python.org/issue15275>
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