I am trying to write a function that has a sympy symbol with a default value, but am not getting what I expect.

Here is my code

import sympy as sy
def addtwo(y = sy.symbols('y', reals = True)):
    return y + 2

x = addtwo()
print(type(x))
print(x)
print(x.subs(y,1))

with output

<class 'sympy.core.add.Add'>
y + 2
y + 2

However, the code

y = sy.symbols('y')
x = addtwo(y)
print(x)
print(x.subs(y,1))

gives the expected output

y + 2
3