Pupeno wrote:
Hello,
I am experiencing a weird behavior that is driving me crazy. I have module
called Sensors containing, among other things:
class Manager:
def getStatus(self) :
print "getStatus(self =%s)" % self
return {"a": "b", "c": "d"}
and then I have another module called SensorSingleton that emulates the
hard-to-code-on-python singleton in this way:
manager = Manager()
print "manager=%s " % manager
def getStatus():
print "getStatus( )"
return manager.getStat us()
and then in some other module, I import SensorSingleton and I do, among
other things:
print SensorSingleton .getStatus()
and the output is more or less like this. First, the manager:
manager: <Sensor.Manag er object at 0xb7b9efec>
### Uh-oh. The code should print "manager=", not "manager:"
>
ok, then
Manager.getStat us(self=<Sensor .Manager object at 0xb77cde8c>) =>
### Uh-oh. The code should print "getStatus(self =blahblahblah" i.e.
without "Manager." in the front.
{"a": "b", "c": "d"}
None
None is the return of SensorSingleton .getStatus(),
### What evidence do you have for that statement?
now, my questions are:
>
- Shouldn't the manager be the same in the first print and the second, that
is, the id is different, shouldn't it be the same ?
### Yes.
- What happened with all the output of SensorSingleton .getStatus() ? there's
no trace of it (but there's output of the method it calls).
### All what output? The only expected output is "getStatus( )"
- Why doesn't the SensorSingleton .getStatus() return the return value of
manager.getStat us(), it's a very straight forward call to it and return it.
If you want help, forget the "more or less" caper -- it's useless. It's
obvious from the above that the output that you describe can *not* have
come from the code fragments that you showed.Cut your 3 modules down to
the bare minimum that still shows the bug. Include copies of those plus
the exact (copy/paste) results of running the test at the OS
command-line (I.e. not in an IDE). Do make sure that none of your
modules are being shadowed or are outdated -- have all 3 in your
current working directory, and delete all .pyc files before running the
test.
What version of Python are you running? 2.3? Which platform?
Below's what I tried -- it's essentially the same as your code, with a
bit more output and with lower-case module names and I didn't bother
with a 2-line calling module. It works as expected.
HTH,
John
C:\junk>python
Python 2.4.3 (#69, Mar 29 2006, 17:35:34) [MSC v.1310 32 bit (Intel)]
on win32
Type "help", "copyright" , "credits" or "license" for more information.
|>>import singleton
[singleton] manager=<sensor s.Manager instance at 0x00AF43A0>
|>>singleton.ge tStatus()
[singleton] entered getStatus()
[sensors]getStatus(self <sensors.Manage r instance at 0x00AF43A0>)
[singleton] stuff = {'a': 'b', 'c': 'd'}
{'a': 'b', 'c': 'd'}
|>>^Z
C:\junk>type sensors.py
class Manager:
def getStatus(self) :
print "[sensors]getStatus(self %s)" % self
return {"a": "b", "c": "d"}
C:\junk>type singleton.py
from sensors import Manager
manager = Manager()
print "[singleton] manager=%s" % manager
def getStatus():
print "[singleton] entered getStatus()"
stuff = manager.getStat us()
print "[singleton] stuff =", stuff
return stuff
8<---
