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.
解决方案
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.
相关文章