How to find all possible combinations from nested list containing list and strings?

Question

I am trying to get all possible pattern from list like:

input_x = ['1', ['2', '2x'], '3', '4', ['5', '5x']]

As we see, it has 2 nested list ['2', '2x'] and ['5', '5x'] here.

That means all possible pattern is 4 (2 case x 2 case), the expect output is:

output1 = ['1','2' , '3', '4',  '5']
output2 = ['1','2x', '3', '4',  '5']
output3 = ['1','2' , '3', '4', '5x']
output4 = ['1','2x', '3', '4', '5x']

I tried to search how to, but I can not find any examples (because of I have no idea about "keyword" to search)

I think python has inner libraries/methods to handle it.

Answer 1

One way to achieve this is via using itertools.product. But for using that, you need to firstly wrap the single elements within your list to another list.

For example, firstly we need to convert your list:

['1', ['2', '2x'], '3', '4', ['5', '5x']]

to:

[['1'], ['2', '2x'], ['3'], ['4'], ['5', '5x']]

This can be done via below list comprehension as:

formatted_list = [(l if isinstance(l, list) else [l]) for l in my_list]
# Here `formatted_list` is containing the elements in your desired format, i.e.:
#    [['1'], ['2', '2x'], ['3'], ['4'], ['5', '5x']]

Now call itertools.product on the unpacked version of the above list:

>>> from itertools import product

#                v  `*` is used to unpack the `formatted_list` list
>>> list(product(*formatted_list))
[('1', '2', '3', '4', '5'), ('1', '2', '3', '4', '5x'), ('1', '2x', '3', '4', '5'), ('1', '2x', '3', '4', '5x')]