Question

如果我有一个包含五个项目的列表，并且我想获得该列表的每个排列，那么如何保持第一个和最后一个项目相同？

同样，五个项目的列表将导致列表的120个排列，其中该列表中将有六个项目，但第一个和最后一个项目将是相同的。以下是我到目前为止所做的工作。任何帮助将不胜感激。

from itertools import permutations
airportlist = ["airport1", "airport2", "airport3", "airport4", "airport5"]

permlist = permutations(airportlist, 5)
print(permlist)
print(list(permlist))

for i in list(permlist):

    newlist = (list(i))

    print(newlist)# getting e.g. ['airport1', 'airport5', 'airport2', 'airport4', 'airport3']

    print(list(i)[0]) # getting (to continue above example) airport1
    newerlist = (list(i).append((list(i)[0])))

    print(newerlist)#getting None but want ['airport1', 'airport5', 'airport2', 'airport4', 'airport3', 'airport1']

这可能吗？

Answer 1

如果我找到了你，你想让第一个和最后一个机场与原始列表保持一致，并生成两者之间元素的排列。在这种情况下，您可以执行类似下面的操作，其中您只为中间的元素生成排列：

>>> from itertools import permutations
>>> airports = ["airport1", "airport2", "airport3", "airport4", "airport5"]
>>> [airports[:1] + list(x) + airports[-1:] for x in permutations(airports[1:-1])]
[['airport1', 'airport2', 'airport3', 'airport4', 'airport5'], ['airport1', 'airport2', 'airport4', 'airport3', 'airport5'], ['airport1', 'airport3', 'airport2', 'airport4', 'airport5'], ['airport1', 'airport3', 'airport4', 'airport2', 'airport5'], ['airport1', 'airport4', 'airport2', 'airport3', 'airport5'], ['airport1', 'airport4', 'airport3', 'airport2', 'airport5']]

<强> 修改：

重新阅读你的问题，我想你可能想要创建排列，开始和结束机场相同，中间的值得到置换，这将非常简单：

>>> combos = [list(x) + [x[0]] for x in permutations(airports)]
>>> for x in combos: print x
['airport1', 'airport2', 'airport3', 'airport4', 'airport5', 'airport1']
['airport1', 'airport2', 'airport3', 'airport5', 'airport4', 'airport1']
... 
... 
['airport5', 'airport4', 'airport3', 'airport1', 'airport2', 'airport5']
['airport5', 'airport4', 'airport3', 'airport2', 'airport1', 'airport5']

Answer 2

嗯，好吧，将每个列表的第一项附加到每个列表中。

from itertools import permutations
airportlist = ["airport1", "airport2", "airport3"]

perms = permutations (airportlist)
newperms = [list (x) + [x[0]] for x in perms]

for element in list (newperms):
    print element

结果是：

['airport1', 'airport2', 'airport3', 'airport1']
['airport1', 'airport3', 'airport2', 'airport1']
['airport2', 'airport1', 'airport3', 'airport2']
['airport2', 'airport3', 'airport1', 'airport2']
['airport3', 'airport1', 'airport2', 'airport3']
['airport3', 'airport2', 'airport1', 'airport3']

Answer 3

我想你想要的是：

[airportlist[:1] + list(i) + airportlist[:1] for i in permutations(airportlist[1:])]

如何将列表的第一项附加到该列表的所有排列的末尾？

3 个答案: