[Tutor] python instances and type

Andre Engels andreengels at gmail.com
Mon Apr 16 10:58:49 CEST 2007

2007/4/16, Adam Pridgen <atpridgen at mail.utexas.edu>:
> Hello,
> Sorry for the long email, but thanks in advance.
> I am not quite sure what is happening, so I have not been able to
> adequately seek a solution via Google, so if this answer is fairly
> easy to find on Google, let me know.  I am not sure how to produce an
> example of my problem without using the python code and classes that I
> have, so I will try to compose an effective  theoretical example
> below.  If there are any clarifications to be made please let me know.
> Basically the problem I am having is obtaining the proper type
> identification from a Python object.  So going through the motions,
> lets say I have 2 types:
> class foo_1:
>    data = ""
> class foo_2:
>   foo_1s={}
> Time goes by and some assignments are performed and foo_2 is populated
> with some foo_1 objects.  Now, I am using the the function below,
> get_class_resolution to get the type of foo_1 and foo_2, and it works
> well when I don't perform any black magic voodoo and simply use after
> the object is created.
> It would return the string "foo_1" for the example below:
> x = foo_1()
> x.data = "boring"
> print type(x), type(x).mro()
> <class 'foo_1'> [<class 'foo_1'>]
> print get_class_resolution(x)
> foo_1

Would it? When I try it out, I get:

>>> class foo_1:
  data = ""

>>> x = foo_1()
>>> x.data = "boring"
>>> print type(x), type(x).mro()
<type 'instance'> [<type 'instance'>, <type 'object'>]
>>> get_class_resolution(x)
[<type 'instance'>, <type 'object'>]
<type 'instance'>

To get your desired behaviour, you need something like:

>>> class foo_1(object):
        data = ""

>>> x = foo_1()
>>> x.data = "boring"
>>> print type(x), type(x).mro()
<class '__main__.foo_1'> [<class '__main__.foo_1'>, <type 'object'>]
>>> get_class_resolution(x)
[<class '__main__.foo_1'>, <type 'object'>]
<class '__main__.foo_1'>
Andre Engels, andreengels at gmail.com
ICQ: 6260644  --  Skype: a_engels

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