What does the @ symbol mean?

PEP documentation: http://legacy.python.org/dev/peps/pep-0318/

Decorators are a way to execute code before and after your code executes. For example:

def decorator(func):
    def inner_func():
        print('executing function now!')
        func()
        print('your function has completed execution!')
    return inner_func

def print_hi():
    print("hello!")
    
decorated_function = decorator(print_hi)
decorated_function()

Because functions are objects, it is possible to pass them around as parameters. The resulting output of running this is as follows:

executing function now.
hello!
your function has completed execution

You can shorten this to be a decorator like so:

from functools import wraps
def decorator(func):
    @wraps(func)
    def inner_func():
        print('executing function now!')
        func()
        print('your function has completed execution!')
    return inner_func
    
@decorator
def printy():
    print("hello!")

this will use the function below it as the func parameter. The resulting output will be the same.