遍历列表并在 Python 中精美地处理 StopIteration

Question

我正在尝试遍历一个列表，当且仅当迭代到达列表末尾时，我需要执行特定操作，请参见下面的示例：

data = [1, 2, 3]

data_iter = data.__iter__()
try:
    while True:
        item = data_iter.next()
        try:
            do_stuff(item)
            break # we just need to do stuff with the first successful item
        except:
            handle_errors(item) # in case of no success, handle and skip to next item
except StopIteration:
    raise Exception("All items weren't successful")

我相信这段代码不是太 Pythonic，所以我正在寻找更好的方法。我认为理想的代码应该如下所示：

data = [1, 2, 3]

for item in data:
    try:
        do_stuff(item)
        break # we just need to do stuff with the first successful item
    except:
        handle_errors(item) # in case of no success, handle and skip to next item
finally:
    raise Exception("All items weren't successful")

欢迎提出任何想法。

Answer 1

您可以在 for 循环之后使用 else，并且该 else 中的代码只有在您没有将 break 退出 for 循环时才会执行：

data = [1, 2, 3]

for item in data:
    try:
        do_stuff(item)
        break # we just need to do stuff with the first successful item
    except Exception:
        handle_errors(item) # in case of no success, handle and skip to next item
else:
    raise Exception("All items weren't successful")

你可以在documentation for the for statement找到这个，相关的部分如下图：

for_stmt ::=  "for" target_list "in" expression_list ":" suite
              ["else" ":" suite]

在第一个套件中执行的 break 语句终止循环，而不执行 elseclause 的套件。