New submission from Maxime LEURENT :
Hello,
I try to use a dictionnary with limited size, and I use class LRU given in docs
on OrderedDict.
Unfortunately this class is, somehow, not working on pop method.
I say somehow because if I do OrderedDict pop method by hand I don't get any
Exception. I do not understand how LRU.__getitem__ is call after del, and why
"value = super().__getitem__(key)" work, when "self.move_to_end(key)" don't
Code tested on python3.7 and python3.8:
from collections import OrderedDict
class LRU(OrderedDict):
'Limit size, evicting the least recently looked-up key when full'
def __init__(self, maxsize=128, *args, **kwds):
self.maxsize = maxsize
super().__init__(*args, **kwds)
def __getitem__(self, key):
value = super().__getitem__(key)
self.move_to_end(key) #<=== Bug here
return value
def __setitem__(self, key, value):
if key in self:
self.move_to_end(key)
super().__setitem__(key, value)
if len(self) > self.maxsize:
oldest = next(iter(self))
del self[oldest]
d = LRU()
d["foo"] = "bar"
d.pop("foo") #<= KeyError on mode_to_send in LRU.__getitem__ method
#pop method by "hand"
d["foo2"] = "bar"
if "foo2" in d :
result = d["foo2"]
del d["foo2"]
print(result) #work fine
--
assignee: docs@python
components: Documentation
messages: 398571
nosy: docs@python, maximeLeurent
priority: normal
severity: normal
status: open
title: LRU class given as example in OrderedDict example not work on pop
versions: Python 3.7
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<https://bugs.python.org/issue44782>
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