使用可变长度字符串的可变长度列表，如何创建所有组合

Question

In python 3, I have a variable length list, where each element of the list is a variable length string. Something like this

['TO', 'G', 'ZDO', 'DEO', 'SGT', 'D', 'Z', 'FT', 'OV']

and I want to iterate over every possible combination of words where the letters that make up the word are from the strings in the list, and the length of the word is the same as the length of the list. So something like this

TGZDSDZFO
TGZDSDZFV
TGZDSDZTO
...
OGOOTDZTO
OGOOTDZTV

I am having trouble coming up with a generic solution for n-sized list.

Answer 1

>>> (''.join(s) for s in itertools.product(*['TO', 'G', 'ZDO', 'DEO', 'SGT', 'D', 'Z', 'FT', 'OV']))
<generator object <genexpr> at 0x7f2a46468f00>
>>> # to demonstrate:
... 
>>> list(itertools.islice((''.join(s) for s in itertools.product(*['TO', 'G', 'ZDO', 'DEO', 'SGT', 'D', 'Z', 'FT', 'OV'])), 3))
['TGZDSDZFO', 'TGZDSDZFV', 'TGZDSDZTO']

Answer 2

As others have suggested, itertools is perhaps the simplest/easiest way to solve this. If you are looking to write your own algorithm however (ie reimplement what itertools does under the hood), then take a look at this:

def allPerms(L, sofar=''):
    if not L:
        print(sofar)
    else:
        for char in L[0]:
            allPerms(L[1:], sofar+char)

Output:

In [97]: L = ['TO', 'G', 'ZDO', 'DEO', 'SGT', 'D', 'Z', 'FT', 'OV']

In [98]: allPerms(L)
TGZDSDZFO
TGZDSDZFV
TGZDSDZTO
TGZDSDZTV
TGZDGDZFO
TGZDGDZFV
TGZDGDZTO
TGZDGDZTV
TGZDTDZFO
TGZDTDZFV
TGZDTDZTO
TGZDTDZTV
TGZESDZFO
TGZESDZFV
TGZESDZTO
TGZESDZTV
TGZEGDZFO
TGZEGDZFV
TGZEGDZTO
TGZEGDZTV
--- truncated ---

EDIT :

As @njzk2 points out , python3's yield-from does a fantastic job of making the output usable:

def allPerms(L, sofar=''):
    if not L: yield sofar
    else:
        for char in L[0]: yield from allPerms(L[1:], sofar+char)

Output:

In [118]: for i in allPerms(L): print(i)
TGZDSDZFO
TGZDSDZFV
TGZDSDZTO
TGZDSDZTV
TGZDGDZFO
TGZDGDZFV
TGZDGDZTO
TGZDGDZTV
TGZDTDZFO
TGZDTDZFV
TGZDTDZTO
TGZDTDZTV
TGZESDZFO
TGZESDZFV
TGZESDZTO
TGZESDZTV
TGZEGDZFO
TGZEGDZFV
TGZEGDZTO
TGZEGDZTV
TGZETDZFO
TGZETDZFV
TGZETDZTO
--- truncated ---

Answer 3

you could use the itertools module to create the permutations of your desired length. combine all the workds to one string and use it in the permutations function

lst = ['TO', 'G', 'ZDO', 'DEO', 'SGT', 'D', 'Z', 'FT', 'OV']
length = len(lst)

combined = ''.join(lst)
all_perms = itertools.permutations(combined, length)
#this will give you something like [('T', 'O', ...), (...),]

print ([''.join(x) for x in all_perms])