[New-bugs-announce] [issue22955] Pickling of methodcaller and attrgetter
Antony Lee
report at bugs.python.org
Thu Nov 27 07:33:03 CET 2014
New submission from Antony Lee:
methodcaller and attrgetter objects seem to be picklable, but in fact the pickling is erroneous:
>>> import operator, pickle
>>> pickle.loads(pickle.dumps(operator.methodcaller("foo")))
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: methodcaller needs at least one argument, the method name
>>> pickle.loads(pickle.dumps(operator.attrgetter("foo")))
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: attrgetter expected 1 arguments, got 0
When looking at the pickle disassembly, it seems that the argument to the constructor is indeed not pickled.
>>> import pickletools; pickletools.dis(pickle.dumps(operator.methodcaller("foo")))
0: \x80 PROTO 3
2: c GLOBAL 'operator methodcaller'
25: q BINPUT 0
27: ) EMPTY_TUPLE
28: \x81 NEWOBJ
29: q BINPUT 1
31: . STOP
highest protocol among opcodes = 2
----------
components: Library (Lib)
messages: 231752
nosy: Antony.Lee
priority: normal
severity: normal
status: open
title: Pickling of methodcaller and attrgetter
versions: Python 3.4
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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue22955>
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