How can I conveniently print an expression?
trotts at llnl.gov
Sun Dec 31 16:41:21 EST 2000
Thanks for the clever trick. It works!
On Sun, Dec 31, 2000 at 07:02:20PM +0100, Jan Dries wrote:
> Issac Trotts wrote:
> > In Python, one might naively try something like
> > def printexpr(expr_string):
> > expr = eval(expr_string)
> > print expr_string+' = '+`expr`
> > which would be used to say things like
> > printexpr('len(sys.argv)')
> > but of course this does not always work because when Python executes
> > eval(expr_string), it assumes that the elements of the expression
> > specified by expr_string are to be found in the global scope.
> > If there were some mechanism that allowed us to access the variables
> > of a calling function from within a called function, then the problem
> > would be solved. Does anyone know of such a mechanism?
> I once came up with a solution for this. The following should do the
> trick for you:
> from sys import exc_info
> def caller_symbols():
> raise StandardError
> except StandardError:
> t = exc_info().tb_frame
> return (t.f_back.f_back.f_globals,t.f_back.f_back.f_locals)
> def printexpr(expr_string):
> caller_globals,caller_locals = caller_symbols()
> expr = eval(expr_string,caller_globals,caller_locals)
> print expr_string+' = '+`expr`
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