get all possible strings given multiple strings

Question

I have multiple strings on different lines where I want to get all of the possible permutations without changing the order:

for example:

er r er
er er r

which would give me:

er r er
er er r
er r r
er er er

Is there a way to do this is python? If this is a duplicate please advise but I was not able to find one.

This is different from questions like Finding all possible permutations of a given string in python where only one string is used

Update [Still does not work]

import itertools

with open(in_file) as f:
    lis = list(f) 

print (lis)
print([' '.join(x) for x in itertools.product(*map(set, zip(*map(str.split, lis))))])

[Error]

[['er', 'r', 'er'], ['er', 'er', 'r']]
Traceback (most recent call last):
File "test.py", line 37, in <module>
print([' '.join(x) for x in itertools.product(*map(set, zip(*map(str.split, S))))])
TypeError: descriptor 'split' requires a 'str' object but received a 'list'

Answer 1

You can zip the splits of these strings and take the cartesion product, e.g.:

>>> import itertools as it
>>> s1, s2 = 'er r er', 'er er r'
>>> {' '.join(x) for x in it.product(*zip(s1.split(), s2.split()))}
{'er er er', 'er er r', 'er r er', 'er r r'}

You can get duplicates so, constructed as a set comprehension.

Updated for an arbitrary number of strings:

>>> import itertools as it
>>> ss = ['er r er', 'er er r', 'ar er r']
>>> {' '.join(x) for x in it.product(*zip(*map(str.split, ss)))}
{'ar er er', 'ar er r', 'ar r er', 'ar r r', 'er er er', 'er er r', 'er r er', 'er r r'}

Note: You could also apply the set to the arguments to product to remove duplicates and it might be quicker depending on the overlaps of the strings, e.g.:

>>> [' '.join(x) for x in it.product(*map(set, zip(*map(str.split, ss))))]
['er r r', 'er r er', 'er er r', 'er er er', 'ar r r', 'ar r er', 'ar er r', 'ar er er']

To read from a file type object:

>>> with open(in_file) as f:
...     lis = list(f)
>>> print([' '.join(x) for x in it.product(*map(set, zip(*map(str.split, lis))))])
['er r r', 'er r er', 'er er r', 'er er er']

Or more compactly:

>>> with open(in_file) as f:
...     print([' '.join(x) for x in it.product(*map(set, zip(*map(str.split, f))))])
['er r r', 'er r er', 'er er r', 'er er er']