On 1/22/20 7:08 AM, Rhodri James wrote:
On 22/01/2020 12:03, Anders Hovmöller wrote:
He was pretty clear in saying he wanted the same thing as in C#. That
no one in this thread seems to have looked that up is really not his
fault in my opinion.
Oh, plenty of people have looked it up. The problem is that it relies
on part of the nature of C# (variables are lvalues) that simply isn't
true in Python, which I don't think the OP realised.
Or to expand on that, in C# and related languages, variable names
actually HOLD some value (which might be a special type of value called
a pointer), and a given object will either be in a specific variable
name, or off somewhere in the heap with no name. We might have a
variable with a pointer value to another object, and there it can be
useful to query the object through that pointer and ask what is the name
of the variable you are in, as we might not know it at the site of usage.
In Python, variables don't hold values, but refer to them. A given value
can easily be referred to by many names equally, and there is no such
thing as a pointer (which gets you to a name) only multiple references
to the same object.
Thus nameof(x) can ONLY be "x" in Python (or an error is x isn't
something that is a name), as at best x is referring to some object, but
that object doesn't have a special name to refer to it that is its
holder. Yes, one example where that linkage might be useful is it
documents in the code that the string value is actually supposed to be
the name of the variable, so a refactoring that changes the variable
should change the string too, such a semantic link between a variable
and its spelling is ill advised, and would only be used in a debugging
environment with something like print("x", x) or some similar purpose
function, and in that context, such prints should not normally be long
lived or are part of long term logging in which case the stability of
the label might actually be preferred to not break parsers for the log
output.
--
Richard Damon
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