I'm trying to use join() in a nested list with an if statement. If the condition is met, I want to combine all indices from [1:-3]. Every time the join() function doesn't join the index.
Input
a = [['a', 'b', 'c', 'd'], ['a', 'b', 'c', 'd', 'e','f','g'], ['a', 'b', 'c', 'd']]
Expected Output
[['a', 'b', 'c', 'd'], ['a', 'b c d', 'e','f','g'], ['a', 'b', 'c', 'd']]
What I have tried:
a = [' '.join(str(inner_list)) for inner_list in a for i in inner_list if len(inner_list) >= 6 ]
I know the for loop is correct because the following code produces true for a[1][0] and iterates through a[][]. To my understanding, the loop is iterating over the correct part but won't join() from the index [1][1] to [1][3]. This is where I'm very confused.
the index
a = [print("true") for inner_list in a for i in inner_list if len(inner_list) >= 6 ]
You need to slice the inner lists in the loop, but also pass the remaining inner lists as they are if they're smaller than 6 items. Here's an example:
lst = [['a', 'b', 'c', 'd'], ['a', 'b', 'c', 'd', 'e', 'f', 'g'], ['a', 'b', 'c', 'd']]
new_lst = [[l[0:1] + [' '.join(l[1:-3])] + l[-3:]] if len(l) >= 6 else l for l in lst]
print(new_lst)
# Output
# [['a', 'b', 'c', 'd'], [['a', 'b c d', 'e', 'f', 'g']], ['a', 'b', 'c', 'd']]
join() takes a list as an argument instead of a string, and also try to refrain from using built in types like list as variable names.