Is def(): a function?????

Answer 1

As Jonathan said, the correct syntax for defining a function in python is:

def function_name():
...

A function that sums two terms and returns that sum is:

def my_sum(x, y):
s = x + y
return s

And can be called as:

ex_sum = my_sum(2, 3)

Which of course lets ex_sum be equal to 5.

Answer 2

No, because you aren't defining def().

def def(): would be a function.