registration.py

# tag::REGISTRATION[]

registry = []  # <1>

def register(func):  # <2>
    print(f'running register({func})')  # <3>
    registry.append(func)  # <4>
    return func  # <5>

@register  # <6>
def f1():
    print('running f1()')

@register
def f2():
    print('running f2()')

def f3():  # <7>
    print('running f3()')

def main():  # <8>
    print('running main()')
    print('registry ->', registry)
    f1()
    f2()
    f3()

if __name__ == '__main__':
    main()  # <9>

# end::REGISTRATION[]