问题描述
可能重复:
在Python中逆序遍历列表
这可能吗?不必就位，只需寻找一种反转元组的方法，以便我可以反向迭代它.
Is this possible? Doesn't have to be in place, just looking for a way to reverse a tuple so I can iterate on it backwards.
推荐答案
有两种惯用的方法:
reversed(x) # returns an iterator
或
x[::-1] # returns a new tuple
由于元组是不可变的，因此无法就地反转元组.
Since tuples are immutable, there is no way to reverse a tuple in-place.
基于@lvc 的注释，由 reversed 返回的迭代器将等效于
Building on @lvc's comment, the iterator returned by reversed would be equivalent to
def myreversed(seq):
for i in range(len(x) - 1, -1, -1):
yield seq[i]
即它依赖于具有已知长度的序列来避免必须实际反转元组.
i.e. it relies on the sequence having a known length to avoid having to actually reverse the tuple.
至于哪个更有效，我怀疑它会是 seq[::-1] 如果你正在使用它并且元组很小，并且 当元组很大时反转，但是python中的性能常常令人惊讶，所以测量一下！
As to which is more efficient, i'd suspect it'd be the seq[::-1] if you are using all of it and the tuple is small, and reversed when the tuple is large, but performance in python is often surprising so measure it!
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