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
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