控制嵌套列表/字符串上的递归 [英] Control recursion on nested lists / strings
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问题描述
假设我有以下输入内容:
Assume I have the following input:
items = [1, 2, [3, 4], (5, 6), 'ciao', range(3), (i for i in range(3, 6))]
,我想对items
执行一些递归操作.
and I want to perform some recursive operation on items
.
为简单起见,假设我要展平项目(但可以是其他项目),一种方法是:
For the sake of simplicity, let's say I want to flatten items (but could be anything else), one way of doing this would be:
def flatten(items, shallow=(str, bytes, bytearray)):
for item in items:
if isinstance(item, shallow):
yield item
else:
try:
yield from flatten(item)
except TypeError:
yield item
这将产生:
print(list(flatten(items)))
[1, 2, 3, 4, 5, 6, 'ciao', 0, 1, 2, 3, 4, 5]
现在如何修改flatten()
,以便产生以下内容(对于任意嵌套级别)?
Now how could I modify flatten()
so that I could produce the following (for arbitrary nesting levels)?
print(list(flatten(items)))
[1, 2, 3, 4, 5, 6, 'c', 'i', 'a', 'o', 0, 1, 2, 3, 4, 5]
推荐答案
只需在浅层检查旁边添加一个长度检查:
Just add a length check next to the shallow check:
if isinstance(item, shallow) and len(item) == 1:
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