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Kirill Smelkov
ZODB
Commits
7687a555
Commit
7687a555
authored
Oct 12, 2008
by
Christophe Combelles
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Removed the preformatted text markers, and added a __docformat__
parent
3828451c
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src/persistent/wref.py
src/persistent/wref.py
+24
-22
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src/persistent/wref.py
View file @
7687a555
...
...
@@ -16,6 +16,8 @@
$Id$
"""
__docformat__
=
"reStructuredText"
from
persistent
import
Persistent
WeakRefMarker
=
object
()
...
...
@@ -28,7 +30,7 @@ class WeakRef(object):
object to be called when the object is removed from the database.
Here's an example. We'll start by creating a persistent object and
a reference to it:
:
a reference to it:
>>> import persistent, ZODB.tests.MinPO
>>> import ZODB.tests.util
...
...
@@ -37,12 +39,12 @@ class WeakRef(object):
>>> ref() is ob
True
The hash of the ref if the same as the hash of the referenced object:
:
The hash of the ref if the same as the hash of the referenced object:
>>> hash(ref) == hash(ob)
True
Two refs to the same object are equal:
:
Two refs to the same object are equal:
>>> WeakRef(ob) == ref
True
...
...
@@ -51,7 +53,7 @@ class WeakRef(object):
>>> WeakRef(ob2) == ref
False
Lets save the reference and the referenced object in a database:
:
Lets save the reference and the referenced object in a database:
>>> db = ZODB.tests.util.DB()
...
...
@@ -60,7 +62,7 @@ class WeakRef(object):
>>> conn1.root()['ref'] = ref
>>> ZODB.tests.util.commit()
If we open a new connection, we can use the reference:
:
If we open a new connection, we can use the reference:
>>> conn2 = db.open()
>>> conn2.root()['ref']() is conn2.root()['ob']
...
...
@@ -68,13 +70,13 @@ class WeakRef(object):
>>> hash(conn2.root()['ref']) == hash(conn2.root()['ob'])
True
But if we delete the referenced object and pack:
:
But if we delete the referenced object and pack:
>>> del conn2.root()['ob']
>>> ZODB.tests.util.commit()
>>> ZODB.tests.util.pack(db)
And then look in a new connection:
:
And then look in a new connection:
>>> conn3 = db.open()
>>> conn3.root()['ob']
...
...
@@ -82,18 +84,18 @@ class WeakRef(object):
...
KeyError: 'ob'
Trying to dereference the reference returns None:
:
Trying to dereference the reference returns None:
>>> conn3.root()['ref']()
Trying to get a hash, raises a type error:
:
Trying to get a hash, raises a type error:
>>> hash(conn3.root()['ref'])
Traceback (most recent call last):
...
TypeError: Weakly-referenced object has gone away
Always explicitly close databases :) :
:
Always explicitly close databases :) :
>>> db.close()
...
...
@@ -142,7 +144,7 @@ class PersistentWeakKeyDictionary(Persistent):
of items is extremely lazy. See below.
We'll start by creating a PersistentWeakKeyDictionary and adding
some persistent objects to it:
:
some persistent objects to it:
>>> d = PersistentWeakKeyDictionary()
>>> import ZODB.tests.util
...
...
@@ -153,23 +155,23 @@ class PersistentWeakKeyDictionary(Persistent):
>>> d[p2] = 2
>>> d[p3] = 3
We'll create an extra persistent object that's not in the dict:
:
We'll create an extra persistent object that's not in the dict:
>>> p4 = ZODB.tests.util.P('p4')
Now we'll excercise iteration and item access:
:
Now we'll excercise iteration and item access:
>>> l = [(str(k), d[k], d.get(k)) for k in d]
>>> l.sort()
>>> l
[('P(p1)', 1, 1), ('P(p2)', 2, 2), ('P(p3)', 3, 3)]
And the containment operator:
:
And the containment operator:
>>> [p in d for p in [p1, p2, p3, p4]]
[True, True, True, False]
We can add the dict and the referenced objects to a database:
:
We can add the dict and the referenced objects to a database:
>>> db = ZODB.tests.util.DB()
...
...
@@ -180,7 +182,7 @@ class PersistentWeakKeyDictionary(Persistent):
>>> conn1.root()['p3'] = p3
>>> ZODB.tests.util.commit()
And things still work, as before:
:
And things still work, as before:
>>> l = [(str(k), d[k], d.get(k)) for k in d]
>>> l.sort()
...
...
@@ -190,7 +192,7 @@ class PersistentWeakKeyDictionary(Persistent):
[True, True, True, False]
Likewise, we can read the objects from another connection and
things still work:
:
things still work:
>>> conn2 = db.open()
>>> d = conn2.root()['d']
...
...
@@ -205,18 +207,18 @@ class PersistentWeakKeyDictionary(Persistent):
[True, True, True, False]
Now, we'll delete one of the objects from the database, but *not*
from the dictionary:
:
from the dictionary:
>>> del conn2.root()['p2']
>>> ZODB.tests.util.commit()
And pack the database, so that the no-longer referenced p2 is
actually removed from the database:
:
actually removed from the database:
>>> ZODB.tests.util.pack(db)
Now if we access the dictionary in a new connection, it no longer
has p2:
:
has p2:
>>> conn3 = db.open()
>>> d = conn3.root()['d']
...
...
@@ -229,7 +231,7 @@ class PersistentWeakKeyDictionary(Persistent):
conn1 and conn2 still have p2, because p2 is still in the caches
for those connections.
Always explicitly close databases :) :
:
Always explicitly close databases :) :
>>> db.close()
...
...
@@ -269,7 +271,7 @@ class PersistentWeakKeyDictionary(Persistent):
del
self
.
data
[
WeakRef
(
key
)]
def
get
(
self
,
key
,
default
=
None
):
"""D.get(k[, d]) -> D[k] if k in D, else d. :
:
"""D.get(k[, d]) -> D[k] if k in D, else d. :
>>> import ZODB.tests.util
>>> key = ZODB.tests.util.P("key")
...
...
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