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Begin by removing the dest file is maybe not the safer approach :-) Here is a new try: begin by renaming the dest file to a new file.
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# use maybe a PRNG instead of a dummy counter or tempfile
def _create_old_filename(filename):
 old = filename + '.old'
 index = 2
 while os.path.exists(old):
 old = filename + '-%s.old' % index
 index += 1
 return old
if os.name in ('nt', 'ce'):
 def atomic_rename(src, dst):
 if os.path.exists(dst):
 old = _create_old_filename(dst)
 rename(dst, old)
 rename(src, dst)
 unlink(old)
 else:
 rename(src, dst)
else:
 atomic_rename = os.rename
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What can we do if "rename(src, dst)" fails?