This is very easy. have a look at the following code -

>>> def f(y):
return str(y**2) + 'x'
>>> f(9)
'81x'

And if you have the value of constant then

def f(y):
x=2
return x*(y**2)
>>> f(2)
8
>>>

Suppose you have a polynomial equation such as

p(x)=x4−4⋅x2+3⋅xp(x)=x4−4⋅x2+3⋅x then in this case :

>>> def p(x):
return x**4 - 4*x**2 + 3*x
>>> p(2)
6