Broadly speaking, this line (488 in today's CVS) in
Python/weakref.c isn't right:

WRAP_UNARY(proxy_int, PyNumber_Int)

because PyNumber_Int will convert from a string
argument.  You can "exploit" this like so:

class U(unicode): pass

u = U("1")
try:
    range(u)
except TypeError:
    print "raised, good"
else:
    print "didn't raise, bad"
import _weakref

try:
    range(_weakref.proxy(u))
except TypeError:
    print "raised, good"
else:
    print "didn't raise, bad"

(prints

raised, good
didn't raise, bad

for me).  I think the fix is PyNumber_Int ->
PyInt_AsLong, but haven't checked that.

Confirmed with rev69546.

Works fine under 3.x.

It's not fixed. range() now uses the tp_index slot, in weakrefs this becomes:
    WRAP_UNARY(proxy_index, PyNumber_Index)
and indeed PyNumber_Index does not accept strings.

But try with time.sleep() instead; here the line
    WRAP_UNARY(proxy_float, PyNumber_Float)
is involved:


import _weakref, time

class U(str): pass
u = U("1")

try:
    time.sleep(u)
except TypeError:
    print("raised, good")
else:
    print("didn't raise, bad")

try:
    time.sleep(_weakref.proxy(u))
except TypeError:
    print("raised, good")
else:
    print("didn't raise, bad")

I find this problem with 3.x and not with 2.x codeline