python – 根据上一个和下一个元素将元素插入到列表中

我试图在元组列表中添加一个新元组(按元组中的第一个元素排序),其中新元组包含列表中上一个元素和下一个元素的元素.

例：

oldList = [(3,10),(4,7),(5,5)]
newList = [(3,5)]

(4,10)由(3,10)和(4,7)之间构建并添加.

Construct (x,y) from (a,y) and (x,b)

我已经尝试使用枚举()插入到特定的位置,但这并不真正让我访问下一个元素.

解决方法

oldList = [(3,5)]

def pair(lst):
    # create two iterators
    it1,it2 = iter(lst),iter(lst)
    # move second to the second tuple
    next(it2)
    for ele in it1:
        # yield original
        yield ele
        # yield first ele from next and first from current
        yield (next(it2)[0],ele[1])

哪个会给你：

In [3]: oldList = [(3,5)]

In [4]: list(pair(oldList))
Out[4]: [(3,5)]

显然,我们需要做一些错误处理来处理不同的可能情况.

如果您愿意,也可以使用单个迭代器：

def pair(lst):
    it = iter(lst)
    prev = next(it)
    for ele in it:
        yield prev
        yield (prev[0],ele[1])
        prev = ele
    yield (prev[0],ele[1])

您可以使用itertools.tee代替调用iter：

from itertools import tee
def pair(lst):
    # create two iterators
    it1,it2 = tee(lst)
    # move second to the second tuple
    next(it2)
    for ele in it1:
        # yield original
        yield ele
        # yield first ele from next and first from current
        yield (next(it2)[0],ele[1])

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