a example of code
def func1(a): 
    def b(*args, **kwargs):
        print('a = ', a)
        output = a(*args, **kwargs)
        output = output ** 2
        print('func1 =', output)
        return output
    return b
@func1
def func2(b):
    output = b + 2
    print('func2 =', output)
    return output
if __name__ == '__main__' :
    output = func2(1)
    print('output = ', output)
results
a =  <function func2 at 0x7f67690f9ae8>
func2 = 3
func1 = 9
output =  9
description
An @ symbol at the beginning of a line is used for class, function and method decorators.
Read more here: PEP 318: Decorators Python Decorators
The most common Python decorators you will run into are: @property @classmethod @staticmethod
If you see an @ in the middle of a line, that is a different thing, matrix multiplication.