Combine elements of a list of lists into a string

November 21, 2022

I have to combine these 2 lists:

dots = [['.', '.', '.', '.', '.', '.', '.', '.', '.'],
 ['.', '.', '.', '.', '.', '.', '.', '.', '.'],
 ['.', '.', '.', '.', '.', '.', '.', '.', '.'],
 ['.', '.', '.', '.', '.', '.', '.', '.', '.'],
 ['.', '.', '.', '.', '.', '.', '.', '.', '.'],
 ['.', '.', '.', '.', '.', '.', '.', '.', '.'],
 ['.', '.', '.', '.', '.', '.', '.', '.', '.'],
 ['.', '.', '.', '.', '.', '.', '.', '.', '.'],
 ['.', '.', '.', '.', '.', '.', '.', '.', '.']]
spaces = [['   ', '   ', '   ', '   ', '   ', '   ', '   ', '   ', '   '],
 ['   ', '   ', '   ', '   ', '   ', '   ', '   ', '   ', '   '],
 ['   ', '   ', '   ', '   ', '   ', '   ', '   ', '   ', '   '],
 ['   ', '   ', '   ', '   ', '   ', '   ', '   ', '   ', '   '],
 ['   ', '   ', '   ', '   ', '   ', '   ', '   ', '   ', '   '],
 ['   ', '   ', '   ', '   ', '   ', '   ', '   ', '   ', '   '],
 ['   ', '   ', '   ', '   ', '   ', '   ', '   ', '   ', '   '],
 ['   ', '   ', '   ', '   ', '   ', '   ', '   ', '   ', '   '],
 ['   ', '   ', '   ', '   ', '   ', '   ', '   ', '   ', '   ']]

I want every dot separeted by a space and turn them into string just like this:

.   .   .   .   .   .   .   .   .
.   .   .   .   .   .   .   .   .
.   .   .   .   .   .   .   .   .
.   .   .   .   .   .   .   .   .
.   .   .   .   .   .   .   .   .
.   .   .   .   .   .   .   .   .
.   .   .   .   .   .   .   .   .
.   .   .   .   .   .   .   .   .

I wrote this code but it only work for the first line:

lists = [a for b in zip(dots[0], spaces[0]) for a in b]
line = ''.join(liste)

I wanted to know how to loop in for every other sublist in these two lists.

>Solution :

You know how to use zip to simultaneously iterate over two lists, so do that and create a list of strings containing a dot and space for each "row":

lines = [
          "".join(
              dot + space 
              for dot, space in zip(row_dots, row_spaces)
          )
          for row_dots, row_spaces in zip(dots, spaces) 
       ]

Then join the individual lines using the newline character '\n'.

output = "\n".join(lines)
print(output)

.   .   .   .   .   .   .   .   .
.   .   .   .   .   .   .   .   .
.   .   .   .   .   .   .   .   .
.   .   .   .   .   .   .   .   .
.   .   .   .   .   .   .   .   .
.   .   .   .   .   .   .   .   .
.   .   .   .   .   .   .   .   .
.   .   .   .   .   .   .   .   .
.   .   .   .   .   .   .   .   .

Of course, you can combine both into a single statement so that you don’t need to create the list of lines:

output = "\n".join(
              "".join(
                  dot + space 
                  for dot, space in zip(row_dots, row_spaces)
              )
              for row_dots, row_spaces in zip(dots, spaces) 
         )