Python中列表补全中的多个语句? [英] Multiple statements in list compherensions in Python?

问题描述

是否可能有类似的东西:

Is it possible to have something like:

list1 = ...

currentValue = 0
list2 = [currentValue += i, i for i in list1]

我尝试过但是没用吗?编写这些的正确语法是什么?

I tried that but didn't work? What's the proper syntax to write those?

打印语句就是一个例子.实际上，我正在循环外增加一个值.

the print statement was an example. Actually I am incrementing a value outside the loop.

推荐答案

声明不能进入Python表达式内部；这是故意从语言中设计出来的复杂功能.对于此问题，请尝试使用 did 使其成为语言(生成器)的一种复杂功能.观看:

Statements cannot go inside of expressions in Python; it was a complication that was deliberately designed out of the language. For this problem, try using a complication that did make it into the language: generators. Watch:

def total_and_item(sequence):
    total = 0
    for i in sequence:
        total += i
        yield (total, i)

list2 = list(total_and_item(list1))

生成器将到目前为止所见项目的运行记录保持一致，并将其作为每个项目的前缀，就像您的示例尝试执行的那样.当然，一个简单的循环可能会更简单，它在顶部创建一个空列表，并且只需多次调用append()即可！ :-)

The generator keeps a running tally of the items seen so far, and prefixes it to each item, just like it looks like you example tries to do. Of course, a straightforward loop might be even simpler, that creates an empty list at the top and just calls append() a lot! :-)

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