unloading a module created with imp.new_module

[Patrick Stinson]

I am defining a single class with a destructor method that prints ‘__del__’, and running that source code string using exec with the module’s dict like so:

import rtmidi
import sys
import types
import time
import gc

s = """                                                                                       
class A:                                                                                      
    def __del__(self):                                                                        
        print('__del__')                                                                      
a = A()                                                                                       
"""

m = types.ModuleType('mine')
exec(s, m.__dict__)
print('deleting...')
m = None
print('done')

and the output is:

deleting...
done
__del__

I the “__del__" to come between “deleting…” and “done”. This is not being run from the interactive interpreter by via a .py file.

> On Nov 23, 2014, at 12:56 AM, Ian Kelly <ian.g.kelly at gmail.com> wrote:
> 
> On Sun, Nov 23, 2014 at 2:48 AM, Ian Kelly <ian.g.kelly at gmail.com> wrote:
>> On Sat, Nov 22, 2014 at 11:49 PM, Patrick Stinson <patrickkidd at gmail.com> wrote:
>>> If I create a module with imp.new_module(name), how can I unload it so that all the references contained in it are set to zero and the module is deleted? deleting the reference that is returned doesn’t seem to do the job, and it’s not in sys.modules, so where is the dangling reference?
>> 
>> How are you determining that the module is not deleted?
> 
> From my testing, using Python 3.4:
> 
>>>> for i in range(5): imp.new_module('spam')
> ...
> <module 'spam'>
> <module 'spam'>
> <module 'spam'>
> <module 'spam'>
> <module 'spam'>
>>>> import gc, types
>>>> [m for m in gc.get_objects() if isinstance(m, types.ModuleType) and m.__name__ == 'spam']
> [<module 'spam'>]
>>>> 42
> 42
>>>> [m for m in gc.get_objects() if isinstance(m, types.ModuleType) and m.__name__ == 'spam']
> []
> 
> In this case one of the created modules was hanging around because it
> was still referenced by the special "_" variable of the interactive
> interpreter. Evaluating a new expression cleared that out and deleted
> the module. Maybe you're seeing the same thing.
> -- 
> https://mail.python.org/mailman/listinfo/python-list

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