Duncan Booth wote:
> Also, of course, vars just needs to be something which quacks like a dict:
> it can do whatever it needs to do such as looking up a database or querying
> a server to generate the value only when it needs it, or even evaluating
> the name as an expression; in the OP's case it could call get_variable.
And in case that sounds difficult, the code is
class VariableGetter:
def __getitem__(self, key):
return get_variable(key)
> Anyway, the question seems to be moot since the OP's definition of 'elegant
> and lazy' includes regular expressions and reinvented wheels.
Your suggestion of subclassing string.Template will also require a
regular expression -- and a fairly hairy one as far as I can work out
from the documentation. There isn't an example and I don't think it's
the easiest way of solving this problem. But if Samuel really wants
backslash escaping it'd be easier to do a replace('$$','$$$$') and
replace('\\$', '$$') (or replace('\\$','\\$$') if he really wants the
backslash to persist) before using the template.
Then, if he really does want to reject single letter variable names,
or names beginning with a backslash, he'll still need to subclass
Template and supply a regular expression, but a simpler one.
> ... and in another message Graham Breed wrote:
> > def get_variable(varname):
> > return globals()[varname]
>
> Doesn't the mere thought of creating global variables with unknown names
> make you shudder?
Not at all. It works, it's what the shell does, and it's easy to test
interactively. Obviously the application code wouldn't look like
that.
Graham
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