python - functools 库的示例不可重现

Question

我正在研究functoolspython中的图书馆。但是，当我从装饰器的文档中复制示例时

@singledispatch

我没有得到与文档中报告的结果相同的结果。

from functools import singledispatch

@singledispatch
def fun(arg, verbose=False):
    if verbose:
        print("Let me just say,", end=" ")
    print(arg)

@fun.register
def _(arg: int, verbose=False):
    if verbose:
        print("Strength in numbers, eh?", end=" ")
    print(arg)

@fun.register
def _(arg: list, verbose=False):
    if verbose:
        print("Enumerate this:")
    for i, elem in enumerate(arg):
        print(i, elem)

应评估为：

>>> fun("Hello, world.")
Hello, world.
>>> fun("test.", verbose=True)
Let me just say, test.
>>> fun(42, verbose=True)
Strength in numbers, eh? 42
>>> fun(['spam', 'spam', 'eggs', 'spam'], verbose=True)
Enumerate this:
0 spam
1 spam
2 eggs
3 spam

但在我的 juypter notebook 中却没有。

>>> fun("Hello, world.")
Hello, world.
>>> fun("test.", verbose=True)
Let me just say, test.
>>> fun(42, verbose=True)
Let me just say, 42
>>> fun(['spam', 'spam', 'eggs', 'spam'], verbose=True)
Let me just say, ['spam', 'spam', 'eggs', 'spam']