在Python 3中是否可以看到generator.next()? [英] Is generator.next() visible in Python 3?

问题描述

我有一个生成序列的生成器，例如:

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:

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，则会出现以下错误:

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

但是，循环迭代器语法确实可以在Python 3中使用

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

我还找不到任何能够解释Python 3行为差异的东西.

解决方案

g.next()已重命名为g.__next__().原因是一致:__init__()和__del__()之类的特殊方法都具有双下划线(在当前情况下为"dunder")，而.next()是该规则的少数例外之一.这已在Python 3.0中修复. [*]

但不要使用 next(g) . /p>

[*]还有其他特殊属性可以解决此问题； func_name，现在是__name__，等.

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

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

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

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'

but, the loop iterator syntax does work in Python 3

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

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

解决方案

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. [*]

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

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

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