CODEWITHSUNDEEP
python
Johnny
Johnny

Reputation: 173

concatenate strings based on ints from a list

I had a similar question here but it's a different issue. I have two lists. list0 is a list of strings and list1 is a list of lists consisting of ints.

        # In this example are 8 strings
list0 = ["Test", "Test2", "More text", "Test123", "ttt", "abc", "okokok", "Hello"]
list1 = [ [0, 1], [2], [3], [4,5,6], [7] ...... ]
        # therefore 8 ints, 0 - 7; it always starts with 0.

There are exact the same number of strings in list0 as ints in list1.

I want to loop through the items of list1 ([0,1], [2], ...) and concatenate the strings from list0 according to the int numbers of the item from list1. So new_list[0]+new_list[1] should beconcatenated, 2 and 3 not, than 4+5+6 should be concatenated and so on... I don't know how to do that in one single for loop since the amount of ints in one item can vary. So what I am looking for is a new concatenated list that should look like this:

           # 0 and 1         2           3        4  5  6          7
new_list = ["TestTest", "More text", "Test123", "tttabcokokok", "Hello"]

How can I do this?

Upvotes: 3

Views: 106

Answers (2)

Jon Clements
Jon Clements

Reputation: 142206

I'd go for operator.itemgetter and a list-comp*, eg:

from operator import itemgetter

list0 = ["Test", "Test2", "More text", "Test123", "ttt", "abc", "okokok", "Hello"]
list1 = [ [0, 1], [2], [3], [4,5,6], [7] ]

new = [''.join(itemgetter(*indices)(list0)) for indices in list1]
# ['TestTest2', 'More text', 'Test123', 'tttabcokokok', 'Hello']

* Well - no I'd go for the list-comp - it's faster and doesn't require an import... Consider this an alternative though...

Upvotes: 4

Martijn Pieters
Martijn Pieters

Reputation: 1123520

Use list comprehensions and str.join():

new_list = [''.join([list0[i] for i in indices]) for indices in list1]

Demo:

>>> list0 = ["Test", "Test2", "More text", "Test123", "ttt", "abc", "okokok", "Hello"]
>>> list1 = [ [0, 1], [2], [3], [4,5,6], [7]]
>>> [''.join([list0[i] for i in indices]) for indices in list1]
['TestTest2', 'More text', 'Test123', 'tttabcokokok', 'Hello']

Upvotes: 9

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