Changed the dict implementation to take "string shortcuts" only when
keys are true strings -- no subclasses need apply. This may be debatable.
The problem is that a str subclass may very well want to override __eq__
and/or __hash__ (see the new example of case-insensitive strings in
test_descr), but go-fast shortcuts for strings are ubiquitous in our dicts
(and subclass overrides aren't even looked for then). Another go-fast
reason for the change is that PyCheck_StringExact() is a quicker test
than PyCheck_String(), and we make such a test on virtually every access
to every dict.
OTOH, a str subclass may also be perfectly happy using the base str eq
and hash, and this change slows them a lot. But those cases are still
hypothetical, while Python's own reliance on true-string dicts is not.
diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index f1af5b9..06631dc 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -1533,8 +1533,8 @@
verify(str(s) == base)
verify(str(s).__class__ is str)
verify(hash(s) == hash(base))
- verify({s: 1}[base] == 1)
- verify({base: 1}[s] == 1)
+ #XXX verify({s: 1}[base] == 1)
+ #XXX verify({base: 1}[s] == 1)
verify((s + "").__class__ is str)
verify(s + "" == base)
verify(("" + s).__class__ is str)
@@ -1758,6 +1758,39 @@
except:
pass
+def str_subclass_as_dict_key():
+ if verbose:
+ print "Testing a str subclass used as dict key .."
+
+ class cistr(str):
+ """Sublcass of str that computes __eq__ case-insensitively.
+
+ Also computes a hash code of the string in canonical form.
+ """
+
+ def __init__(self, value):
+ self.canonical = value.lower()
+ self.hashcode = hash(self.canonical)
+
+ def __eq__(self, other):
+ if not isinstance(other, cistr):
+ other = cistr(other)
+ return self.canonical == other.canonical
+
+ def __hash__(self):
+ return self.hashcode
+
+ verify('aBc' == cistr('ABC') == 'abc')
+ verify(str(cistr('ABC')) == 'ABC')
+
+ d = {cistr('one'): 1, cistr('two'): 2, cistr('tHree'): 3}
+ verify(d[cistr('one')] == 1)
+ verify(d[cistr('tWo')] == 2)
+ verify(d[cistr('THrEE')] == 3)
+ verify(cistr('ONe') in d)
+ verify(d.get(cistr('thrEE')) == 3)
+
+
def all():
lists()
dicts()
@@ -1794,6 +1827,7 @@
inherits()
keywords()
restricted()
+ str_subclass_as_dict_key()
all()