在 Python 3 中 generator.next() 是可见的吗?

问题描述

我有一个生成系列的生成器，例如:

I have a generator that generates a series, for example:

def triangle_nums():
    '''Generates a series of triangle numbers'''
    tn = 0
    counter = 1
    while True:
        tn += counter
        yield tn
        counter += + 1

在 Python 2 中，我可以进行以下调用:

In Python 2 I am able to make the following calls:

g = triangle_nums()  # get the generator
g.next()             # get the next value

但是在 Python 3 中，如果我执行相同的两行代码，则会收到以下错误:

however in Python 3 if I execute the same two lines of code I get the following error:

AttributeError: 'generator' object has no attribute 'next'

但是，循环迭代器语法在 Python 3 中确实有效

but, the loop iterator syntax does work in Python 3

for n in triangle_nums():
    if not exit_cond:
       do_something()...

我还没有找到任何东西来解释 Python 3 的这种行为差异.

I haven't been able to find anything yet that explains this difference in behavior for Python 3.

推荐答案

g.next() 已重命名为 g.__next__().这样做的原因是一致性:像 __init__() 和 __del__() 这样的特殊方法都有双下划线(或当前白话中的dunder")，而 .next() 是该规则的少数例外之一.这已在 Python 3.0 中修复.[*]

g.next() has been renamed to g.__next__(). The reason for this is consistency: special methods like __init__() and __del__() all have double underscores (or "dunder" in the current vernacular), and .next() was one of the few exceptions to that rule. This was fixed in Python 3.0. [*]

但不要调用 g.__next__()，而是使用 next(g).

But instead of calling g.__next__(), use next(g).

[*] 还有其他特殊属性已得到此修复；func_name，现在是 __name__，等

[*] There are other special attributes that have gotten this fix; func_name, is now __name__, etc.

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