Inserting Elements of 1D array to specific location in 2D array

Question

Attempting to combine 1 & 2 dimensional list/arrays containing strings using the insert() method.

However getting a specific element from the 1D list and placing that into a specific location within the 2D list is where Im stuck.

Here is a simplified version of what the goal is;

#2D list/array
list1= [['a1','b1'], ['a2','b2'] , ['a3','b3']]

#1D list/array
list2= ['c3','c2','c1']

#desired output
list1= [['a1','b1','c1'], ['a2','b2','c2'] , ['a3','b3','c3']]

Here is the isolated block of code from the script which Im trying to attempt this with;

#loop through 1D list with a nested for-loop for 2D list and use insert() method.
#using reversed() method on list2 as this 1D array is in reverse order starting from "c3 -> c1"
#insert(2,c) is specifying insert "c" at index[2] location of inner array of List1

for c in reversed(list2):
    for letters in list1:
        letters.insert(2,c)

print(list1)

output of the code above;

[['a1', 'b1', 'c3', 'c2', 'c1'], ['a2', 'b2', 'c3', 'c2', 'c1'], ['a3', 'b3', 'c3', 'c2', 'c1']] 

What is the best & most efficient way to go about returning the desired output? Should I use the append() method rather than insert() or should i introduce list concatenation before using any methods?

Any insight would be appreciated!

Answer 1

As discussed in the comments, you can achieve this via a list comprehension using enumerate or zip. You can use enumerate to get the index and sublist from list1, using the index to select the appropriate value from list2 to append to each sublist:

list1 = [l1 + [list2[-i-1]] for i, l1 in enumerate(list1)]

or you can zip together list1 and the reversed list2:

list1 = [l1 + [l2] for l1, l2 in zip(list1, list2[::-1])]

Or you can just use a simple for loop to modify list1 in place:

for i in range(len(list1)):
    list1[i].append(list2[-i-1])

For all of these the output is:

[['a1', 'b1', 'c1'], ['a2', 'b2', 'c2'], ['a3', 'b3', 'c3']]