从列表中获取n长度的所有组合

Question

I was wondering how to get all the possible combinations from a list with n-length from python. But there is one catch. It's hard for me to explain as English is not my native language. So I give an example:

If I have a list:

my_List = [1, 2, 3, 4]

I want it to get an output of with length 3 to be

(1, 1, 1)
(1, 1, 2)
(1, 1, 3)
(1, 1, 4)
etc etc

But I do NOT want to have repeated lists. By that I mean, if I already have

(1, 1, 2)

I do not have any need for

(1, 2, 1) and
(2, 1, 1)

Does that make any sence? Any help woudl be much apreciated

Answer 1

Use itertools.combinations_with_replacement :

>>> import itertools
>>> my_List = [1, 2, 3, 4]
>>> for xs in itertools.combinations_with_replacement(my_List, 3):
...     print(xs)
...
(1, 1, 1)
(1, 1, 2)
(1, 1, 3)
(1, 1, 4)
(1, 2, 2)
(1, 2, 3)
...