len("asdf")

len([1, 2, 3, 4, 5])

[1, 2, 3, 4, 5].__len__()

def p(arg):
    if isinstance(arg, list):
        print("a list:")
        for e in enumerate(arg):
            print("{}: {}".format(*e))
    elif isinstance(arg, str):
        print("a string:", arg)
        
    else:
        print("an unknown object:", repr(arg))

p([1, 2, 3, 4, 5]), p({})

from functools import singledispatch

@singledispatch
def pp(arg, verbose=False):
    print("an object:", repr(arg))
    

pp("asdf"), pp(123), pp([])

@pp.register(list)
def pp_list(arg):
    print("a list:")
    for e in enumerate(arg):
        print("{}: {}".format(*e))

pp("asfd")

pp([1, 2, 3, 4, 5])

@pp.register(int)
@pp.register(float)
def pp_number(obj):
    print("a number:", obj)

pp(1)


pp(1.0)


pp.register(type(None), lambda _: print("nothing"))

pp(None)


pp.dispatch(list)

pp.dispatch(int)

pp.dispatch(dict)

pp.registry.keys()

from pkgutil import simplegeneric