Test the head of expression

[Anton Makarov]

Hi there.
I am trying to test the root of expression tree, for example:
expr = sympify("somefunc(2-5)")
if expr.func.name =="somefunc":
    call_func_1()
else:
    call_func_2()

It works just fine, but when I change the expression, for example, to
expr = sympify("5+6")

Code throws the exception, with error:

AttributeError: type object 'Add' has no attribute 'name'

I don't understand, why Add class has no attribute "name". Or what attribute has all the classes, so I can test the head of any expression without code exception?

What code should I write ?

[Anton Makarov]

And one more question: what sympy expression tree classes have the 'name' attribute?

пятница, 5 августа 2022 г. в 21:40:08 UTC+3, Anton Makarov:

[Aaron Meurer]

Your somefunc is sympified as Function('somefunc'), so you could do

somefunc = Function('somefunc')
if expr.func == somefunc:
...

If you want to test for undefined functions generically you can use

from sympy.core.function import UndefinedFunction
if isinstance(expr.func, UndefinedFunction):
...

Aaron Meurer

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