通过迭代可调用列表的问题 [英] Issue with iterating through list of callable

问题描述

我有一个问题迭代python列表中的python。可卡因应该被称为一个字符串生成器。当前的行为是列表中的最后一个可调用被调用多次，因为列表中有可调用的元素。我当前的代码：

pre $ for list_of_callables：
strings =（m（s）for s in strings）


在上面的代码中，字符串最初是'Generator'类型。我也尝试了以下内容：

pre $ 对于范围（len（list_of_callables））：
strings =（list__of_callables [我]（S）的字符串）


这也没有奏效，但是当我不回顾可以调用的方法，只需调用它就可以了：

  strings =（list_of_callables [0]（s）for s）in 
 string =（list_of_callables [1]（s）for s in string）
  

<对于我来说这似乎很奇怪，因为上面的内容应该和for循环相同。

在此先感谢您的帮助和建议:)

$ div class =h2_lin>解决方案

  strings =（m（s）for s in strings）
  

这实际上并不会调用您的可调用函数。它创建一个生成器表达式，稍后将调用 m ，使用任何 m 碰巧稍后

在循环之后， m 是最后的可调用对象。当你试图从 strings 检索一个元素时，所有嵌套的genexps都会查找 m 来计算一个值，所有找到最后一个可调用。
$ b $你可以通过使用 itertools.imap 而不是genexp来解决这个问题：

p>

  strings = itertools.imap（m，strings）
  

I am having an issue with iterating over a list of callables in python. The callables are supposed to be called on a generator of strings. The current behaviour is that the last callable in the list is called as many times as there are callables in the list. My current code:

for m in list_of_callables:
    strings = (m(s) for s in strings)

In the above code strings is initially of type 'Generator'. I have also tried the following:

for i in range(len(list_of_callables)):
    strings = (list__of_callables[i](s) for s in strings)

This has not worked either, but when I don't loop over the callables and simply call them it works just fine:

strings = (list_of_callables[0](s) for s in strings)
strings = (list_of_callables[1](s) for s in strings)

This seems strange to me as the above should be equivalent to the for loop.

Thanks in advance for your help and suggestions :).

解决方案

strings = (m(s) for s in strings)

This doesn't actually call your callable. It creates a generator expression that will call m later, using whatever m happens to be later.

After the loop, m is the final callable. When you try to retrieve an element from strings, all those nested genexps look up m to compute a value, and they all find the last callable.

You could fix this by using itertools.imap instead of a genexp:

strings = itertools.imap(m, strings)

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