Question

在阅读文件时，我知道可以通过next()获取下一行，但是有一个函数，例如，prev()可以转到上一行吗？

与此类似，在循环浏览文件时，是否可以在目标行之后获取第二行？ next()只会在字符串后面返回该行。

Answer 1

不，没有对手。您可以将以前的行存储在变量中：

prev = None
for something in an_iterator:
    # do something with prev
    prev = something

对于多件商品，您可以使用collections.deque() object：

from collections import deque

five_prev = deque(an_iterator, maxlen=5)
for something in an_iterator:
    five_lines_back = five_prev.popleft()
    # ...
    five_prev.append(something)

在从迭代中检索它之前，您无法知道接下来会发生什么，但您当然可以跟踪之前的内容。

您不仅限于拨打next()一次;如果您需要从iterable中检索两行，请两次调用next()，或使用next() Array ( [11] => Array ( [0] => Array ( [count] => 2 [price] => 1000 [total] => 2000 ) [1] => Array ( [count] => 0 [price] => 124 [total] => 0 ) [2] => Array ( [count] => 0 [price] => 1000 [total] => 0 ) [3] => Array ( [count] => 0 [price] => 2345 [total] => 0 ) ) [12] => Array ( [0] => Array ( [count] => 0 [price] => 1000 [total] => 0 ) [1] => Array ( [count] => 1 [price] => 124 [total] => 124 ) [2] => Array ( [count] => 0 [price] => 1000 [total] => 0 ) [3] => Array ( [count] => 0 [price] => 2345 [total] => 0 ) ) )来检索多个项目。

是否有next（）的对应物？

1 个答案: