PyDict_*() refcount assumptions

[sndive]

i checked this: http://svn.python.org/projects/python/trunk/Doc/data/refcounts.dat
and it seems that
PyDict_SetItem incref the value being added and the key
and PyDict_DelItem does not decrement any refcounts
so i have to do so manually for the key and for the data( by calling
PyDict_GetItem first).
Did i decipher the dat file correctly and is there a wrapper for
DelItem that reverses
the refcounts to what they were before the SetItem or do i have have
to do 2 calls for
deletion?

 

[Gabriel Genellina]

i checked this:
http://svn.python.org/projects/python/trunk/Doc/data/refcounts.dat
and it seems that
PyDict_SetItem incref the value being added and the key
and PyDict_DelItem does not decrement any refcounts
so i have to do so manually for the key and for the data( by calling
PyDict_GetItem first).

Looking at the implementation, PyDict_DelItem decrements both the previous
key *and* its associated value. The stored key might not be the same as
the parameter; consider this example:

d = {}
d[1] = 'a'
del d[1.0]
assert d == {}

I think the refcounts.dat file is more intended for automatic tools than
for humans. It cannot express the fact that PyDict_DelItem decrements both
the stored key and its associated value, by example. This is a limitation
of the chosen format. PyDict_Clear decrements a lot of references but
there is no way to express that in the refcounts.dat file.

Did i decipher the dat file correctly and is there a wrapper for
DelItem that reverses
the refcounts to what they were before the SetItem or do i have have
to do 2 calls for
deletion?

You don't need any wrapper: PyDict_SetItem and PyDict_DelItem do "the
right thing" with their reference counts, so there is no need of
additional increments/decrements.