Re: Printing the name of a variable
Stephen Boulet stephen.bou...@gmail.com writes: Does an arbitrary variable carry an attribute describing the text in its name? I'm looking for something along the lines of: x = 10 print x.name 'x' Perhaps the x.__getattribute__ method? Thanks. The first thing is... what is your use case for this? I'd guess that you probably don't want to do this even if you think you do :) The thing referred to by x is the number 10. When you write x.name (or property) then you're dealing with the number 10, not with some representation of the variable x. There may be many variables (or none) that refer to that number at any given time during the execution of your code... and the object itself knows nothing about any of these. A good way to think about variable lookup is as a dictionary . It's something like variables['x'].name. Once the varables['x'] bit has been evaluated the link with 'x' is gone... we just have the result of the lookup. If you want to know how it actually works, then read up on python namespaces and scopes, e.g. here: http://www.network-theory.co.uk/docs/pytut/PythonScopesandNameSpaces.html. -- http://mail.python.org/mailman/listinfo/python-list
Re: Printing the name of a variable
On Sep 9, 9:11 pm, Albert Hopkins mar...@letterboxes.org wrote: On Thu, 2010-09-09 at 12:43 -0700, Stephen Boulet wrote: Does an arbitrary variable carry an attribute describing the text in its name? I'm looking for something along the lines of: x = 10 print x.name 'x' Perhaps the x.__getattribute__ method? Thanks. Variables are not objects and so they have no attributes. You can't really de-reference the object being referenced as it can potentially contain multiple references, but an innacurate way of doing this would be, e.g. x = [1, 2, 3] y = x g = globals() varnames = [i for i in g if g[i] is x] ['x', 'y'] But this cries the question: why do you want to do this? And usually that question is asked when someone thinks that a: you shouldn't need to do this and b: whatever the desired effect there is probably a better way of accomplishing it. I have in the past wondered about creating a kind of graphical debugger, that rendered representations of all the objects in globals and/or locals, to give you a visual representation of your variables and their states. Would this be a valid use case to try and look up the variable names which reference various in-memory objects? -- http://mail.python.org/mailman/listinfo/python-list
Re: Printing the name of a variable
On 9 September 2010 20:43, Stephen Boulet stephen.bou...@gmail.com wrote: Does an arbitrary variable carry an attribute describing the text in its name? I'm looking for something along the lines of: x = 10 print x.name 'x' http://effbot.org/pyfaq/how-can-my-code-discover-the-name-of-an-object.htm -- Cheers, Simon B. -- http://mail.python.org/mailman/listinfo/python-list
Printing the name of a variable
Does an arbitrary variable carry an attribute describing the text in its name? I'm looking for something along the lines of: x = 10 print x.name 'x' Perhaps the x.__getattribute__ method? Thanks. -- http://mail.python.org/mailman/listinfo/python-list
Re: Printing the name of a variable
On Thu, 2010-09-09 at 12:43 -0700, Stephen Boulet wrote: Does an arbitrary variable carry an attribute describing the text in its name? I'm looking for something along the lines of: x = 10 print x.name 'x' Perhaps the x.__getattribute__ method? Thanks. Variables are not objects and so they have no attributes. You can't really de-reference the object being referenced as it can potentially contain multiple references, but an innacurate way of doing this would be, e.g. x = [1, 2, 3] y = x g = globals() varnames = [i for i in g if g[i] is x] ['x', 'y'] But this cries the question: why do you want to do this? And usually that question is asked when someone thinks that a: you shouldn't need to do this and b: whatever the desired effect there is probably a better way of accomplishing it. -- http://mail.python.org/mailman/listinfo/python-list
Re: Printing the name of a variable
On 9/9/2010 3:43 PM, Stephen Boulet wrote: In Python, 'variable' is a synonym for name and identifier,' An object can have 0 to many names attached to it. An object can also be a member of 0 to many collections. Modules, classes, and functions have 'definition name' strings attached to them as their .__name__ attribute. This attribute is used to display the 'value' of these objects, as in def f(): pass f function f at 0x00F05420 The __name__ attribute is also used in the idiom if __name__ == '__main__': print(I am the main module) I am the main module to determine if a module is being run as the main module as imported into another module. -- Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: Printing the name of a variable
Albert Hopkins mar...@letterboxes.org writes: On Thu, 2010-09-09 at 12:43 -0700, Stephen Boulet wrote: Does an arbitrary variable carry an attribute describing the text in its name? Variables are not objects and so they have no attributes. Another way of thinking about is that there are no variables, only bindings between references and objects. The bindings are not directly accessible and have no attributes. Any object may have zero, one, or many references to it at any given time. Those references might be names, or something else (such as an index in a container). Python does nothing to make the references accessible to the object. If you want to keep track of such associations, you need to employ some mechanism to do so explicitly. You can't really de-reference the object being referenced as it can potentially contain multiple references Including the case where an object has no explicit references beyond the current expression. But this cries the question: why do you want to do this? And usually that question is asked when someone thinks that a: you shouldn't need to do this and b: whatever the desired effect there is probably a better way of accomplishing it. To anticipate a common case: if you feel you need to maintain a mapping between names and objects, Python's built-in mapping type is ‘dict’; use that. -- \ “If you do not trust the source do not use this program.” | `\—Microsoft Vista security dialogue | _o__) | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Re: Printing the name of a variable
Stephen Boulet wrote: Does an arbitrary variable carry an attribute describing the text in its name? I'm looking for something along the lines of: x = 10 print x.name 'x' Perhaps the x.__getattribute__ method? Thanks. Hmm. Recent scholarship suggests that the Iliad and the Odyssey may not have been written by Homer, but by someone else with the same name. Mel. -- http://mail.python.org/mailman/listinfo/python-list
