Converting list of list of strings into list of list of integers

You may try the following list comprehension:

output = [[int(x) for x in re.findall(r'\d+', y[0])] for y in listX]
print(output)

This prints:

[[0, 0, 0, 3, 0, 4, 0, 3], [0, 0, 0, 0, 0, 3, 0, 7],
 [0, 0, 1, 0, 0, 5, 0, 4], [0, 0, 0, 1, 3, 1, 0, 5],
 [1, 1, 1, 0, 0, 0, 2, 5], [0, 0, 0, 1, 1, 5, 0, 3],
 [0, 0, 0, 5, 3, 0, 0, 2]]

This uses a nested list comprehension. The outer comprehension feeds one-element CSV integer strings into the inner comprehension. The inner list comprehension uses re.findall to find integers inside the CSV list, one at a time.

You need to firs split every string you have listX[i].split(",") and then apply the casting

If you have a list of lists with more than a single item you could try the following (nested) list comprehension:

output = [list(map(int, y.split(','))) for x in listX for y in x]

If know your lists contain only a single item, all you'll need is:

output = [list(map(int, x[0].split(','))) for x in listX]

Given your input is

[['0,0,0,3,0,4,0,3'], ['0,0,0,0,0,3,0,7'], 
 ['0,0,1,0,0,5,0,4'], ['0,0,0,1,3,1,0,5'], 
 ['1,1,1,0,0,0,2,5'], ['0,0,0,1,1,5,0,3'], 
 ['0,0,0,5,3,0,0,2']]

Let us start off by splitting it at , using the split method and dumping the whole content into a temporary array say x. The code is as follows-

x=[]
[[x.append(j.split(",")) for j in i] for i in input]
print(x)

The print(x) statement is used solely for debugging & understanding how that part of my code works. You can remove it as seen fit. Now we perform the conversion of lists of strings to lists of integers and store it in the variable say 'y'. The code is as follows -

y = [[int(j) for j in i] for i in x]
print(y)

My in-place solution:

listX = list(map(lambda x: list(int(y) for y in x[0].split(',')), listX))