Use **kwargs with compiled expression

[mhechthz]

Is it possible, to use **kwargs on compiled expressions?

Currently I get always error like

    result = compiled_expr.run(a=a, b=b, c=c)  
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: number of inputs doesn't match program

or

    result = compiled_expr.run({'a': a, 'b': b, 'c': c})
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: number of inputs doesn't match program

or

    result = compiled_expr.run(**kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: number of inputs doesn't match program

[gdementen]

Unsure about this, I assume it does, even though I never used the library like that but the error you are seeing is probably because your expression contains more (or less?) variables than the 3 you are passing.

[mhechthz]

Sorry. Forgot to add the expression. Take this full code:

expr  = "2*a-3*b+4*c"

cexpr = ne.NumExpr(expr)

try: 
    print("V1:",cexpr(5,1,6))
except Exception as ex: 
    print("V1:",ex)

try: 
    print("V2:",cexpr(a=5,b=1,c=6))
except Exception as ex: 
    print("V2:",ex)


try: 
    kwargs = {'a':5,'b':1,'c':6}
    print("V3:",cexpr(**kwargs))
except Exception as ex: 
    print("V3:",ex)


try: 
    args = (5,1,6)
    print("V4:",cexpr(*args))
except Exception as ex: 
    print("V4:",ex)

results in

V1: 31.0
V2: number of inputs doesn't match program
V3: number of inputs doesn't match program
V4: 31.0

So named arguments seem to be impossible. I wanted to check if I can get a faster replacement for eval for arbitrary functions given as string with an allowed set of variables in an arbitrary order.

[mhechthz]

Ok. This works and is acceptable for me:

cnames = cexpr.input_names
kwargs = {'a':5,'b':1,'c':6}
try: 
    args = (kwargs[name] for name in cnames)
    print("V4:",cexpr(*args))
except Exception as ex: 
    print("V4:",ex)