Message371813
PR 20960 (_bz2 module) triggers an interesting question. The effect of converting a static type to a heap type on pickle, especially for protocols 0 and 1.
pickle.dumps(o, 0) calls object.__reduce__(o) which calls copyreg._reduce_ex(o, 0).
copyreg._reduce_ex() behaves differently on heap types:
...
for base in cls.__mro__:
if hasattr(base, '__flags__') and not base.__flags__ & _HEAPTYPE:
break
else:
base = object # not really reachable
...
There are 3 things which impacts serialization/deserialization:
- Py_TPFLAGS_HEAPTYPE flag in the type flags
- Is __new__() overriden in the type?
- Py_TPFLAGS_BASETYPE flag in the type flags
Examples:
* In Python 3.7, _random.Random() cannot be serialized because it's a static type (it doesn't have (Py_TPFLAGS_HEAPTYPE)
* In master, _random.Random() cannot be deserialized because _random.Random() has __new__() method (it's not object.__new__()) |
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Date |
User |
Action |
Args |
2020-06-18 14:06:36 | vstinner | set | recipients:
+ vstinner, phsilva, skrah, eric.snow, corona10, pablogsal, shihai1991, erlendaasland |
2020-06-18 14:06:36 | vstinner | set | messageid: <1592489196.72.0.133874484646.issue40077@roundup.psfhosted.org> |
2020-06-18 14:06:36 | vstinner | link | issue40077 messages |
2020-06-18 14:06:36 | vstinner | create | |
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