is __self__ an implementation detail
A gentoo developer reported a symlink loop problem in reportlab's setup.py where we search for specific headers. The 'fixed' function looks like this def findFile(root, wanted, followlinks=True): visited = set() for p, D, F in os.walk(root,followlinks=followlinks): #scan directories to check for prior visits #use dev/inode to make unique key SD = [].append for d in D: dk = os.stat(pjoin(p,d)) dk = dk.st_dev, dk.st_ino if dk not in visited: visited.add(dk) SD(d) D[:] = SD.__self__ #set the dirs to be scanned for fn in F: if fn==wanted: return abspath(pjoin(p,fn)) the fix is reported to have worked, but the developer is querying the lifting of SD.append using the construct SD = [].append loop involving appends to the list ..... D[:] = SD.__self__ his objection was that using __self__ might be implementation sensitive. I cannot tell from the documentation (eg https://docs.python.org/3.10/reference/datamodel.html) if these magic methods are part of python or of the implementation. On the other hand as a longtime python programmer I wonder if such simple cases are already optimized out in the produced bytecode; for years I have been avoiding s += 'string' and only recently found out that it was handled as a special case. -- Robin Becker
It's documented in stdtypes.rst, so I think it's part of the standard library. I think it's unnecessarily obfuscated though. On Mon, Mar 28, 2022 at 8:44 AM Robin Becker <robin@reportlab.com> wrote:
A gentoo developer reported a symlink loop problem in reportlab's setup.py where we search for specific headers.
The 'fixed' function looks like this
def findFile(root, wanted, followlinks=True): visited = set() for p, D, F in os.walk(root,followlinks=followlinks): #scan directories to check for prior visits #use dev/inode to make unique key SD = [].append for d in D: dk = os.stat(pjoin(p,d)) dk = dk.st_dev, dk.st_ino if dk not in visited: visited.add(dk) SD(d) D[:] = SD.__self__ #set the dirs to be scanned for fn in F: if fn==wanted: return abspath(pjoin(p,fn))
the fix is reported to have worked, but the developer is querying the lifting of SD.append using the construct
SD = [].append loop involving appends to the list ..... D[:] = SD.__self__
his objection was that using __self__ might be implementation sensitive.
I cannot tell from the documentation (eg https://docs.python.org/3.10/reference/datamodel.html) if these magic methods are part of python or of the implementation.
On the other hand as a longtime python programmer I wonder if such simple cases are already optimized out in the produced bytecode; for years I have been avoiding s += 'string' and only recently found out that it was handled as a special case. -- Robin Becker _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-leave@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/3TAF3LR3... Code of Conduct: http://python.org/psf/codeofconduct/
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Guido van Rossum -
Robin Becker