[Tutor] Interesting problem

[Smith, Jeff]

Here would be the usage:

myinst = MyClass()
print myinst.getprops_as_dict()

would print

{'var1': 1, 'var2': 2, 'var3': 3}

Needless to say I want the instance values which might be different for
each instance.  I know that I could code it brute force, but I want to
be able to add properties without having to remember to update
getprops_as_dict().

For those who are interested, the dictionary created by
getprops_as_dict() will be fed to string.Template.substitute

Jeff

-----Original Message-----
From: tutor-bounces at python.org [mailto:tutor-bounces at python.org] On
Behalf Of Kent Johnson
Sent: Thursday, June 23, 2005 3:17 PM
To: Python Tutor
Subject: Re: [Tutor] Interesting problem

Still not that clear. What do you want to see when you call
MyClass().getprops_as_dict() ?

Maybe this will give you some ideas:

 >>> class MyClass:
 ...     def __init__(self, val1, val2):
 ...         self._var1 = val1
 ...         self._var2 = val2
 ...     var1 = property(lambda s: s._var1)
 ...     var2 = property(lambda s: s._var2)
 ...     def _var3(self):
 ...         return self._var1 + self._var2
 ...     var3 = property(_var3)
 ...     def getprops_as_dict(self):
 ...         d = dict(self.__dict__)
 ...         return d
 ...
 >>> m=MyClass(1,2)

Using just m.__dict__:

 >>> m.getprops_as_dict()
{'_var2': 2, '_var1': 1}

The inspect module might be some help:

 >>> import inspect
 >>> for k, v in inspect.getmembers(m):
 ...   print k, '=', v
 ...
__doc__ = None
__init__ = <bound method MyClass.__init__ of <__main__.MyClass instance
at 0x008DD918>> __module__ = __main__ _var1 = 1 _var2 = 2 _var3 = <bound
method MyClass._var3 of <__main__.MyClass instance at 0x008DD918>>
getprops_as_dict = <bound method MyClass.getprops_as_dict of
<__main__.MyClass instance at 0x008DD918>> var1 = 1 var2 = 2 var3 = 3


This inspects the class for actual properties and shows their values. It
won't print simple attributes (in m.__dict__) or attributes defined by
user-defined descriptors though:

 >>> for p in dir(m.__class__):
 ...   pp = getattr(m.__class__, p)
 ...   if isinstance(pp, property):
 ...     print p, '=', getattr(m, p)
 ...
var1 = 1
var2 = 2
var3 = 3

Kent

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