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save_tuple(): Minor rewriting, and added a comment about the subtlety

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created by recursive tuples.
This commit is contained in:
Tim Peters 2003-01-28 02:09:55 +00:00
parent 209ad95b00
commit f558da0f90
1 changed files with 13 additions and 8 deletions
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21
Lib/pickle.py
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@ -454,21 +454,26 @@ class Pickler:
save = self.save save = self.save
memo = self.memo memo = self.memo
d = id(object)
write(MARK) write(MARK)
for element in object: for element in object:
save(element) save(element)
if len(object) and d in memo: if object and id(object) in memo:
# Subtle. d was not in memo when we entered save_tuple(), so
# the process of saving the tuple's elements must have saved
# the tuple itself: the tuple is recursive. The proper action
# now is to throw away everything we put on the stack, and
# simply GET the tuple (it's already constructed). This check
# could have been done in the "for element" loop instead, but
# recursive tuples are a rare thing.
get = self.get(memo[id(object)][0])
if self.bin: if self.bin:
write(POP_MARK + self.get(memo[d][0])) write(POP_MARK + get)
return else: # proto 0 -- POP_MARK not available
write(POP * (len(object) + 1) + get)
write(POP * (len(object) + 1) + self.get(memo[d][0]))
return return
# No recursion (including the empty-tuple case).
self.write(TUPLE) self.write(TUPLE)
self.memoize(object) self.memoize(object)