Файл: в матрице положительные элементы заменить на единичные, а отрицательные обнулить

import random
m,n = 6,7
matr = [[random.randrange(0,7) for y in range(m)] for x in range(n)]
f = open('out.txt','w')
f.write(str(matr))
f.close()

res = []
with open('input1.txt') as f:
    for line in f:
        res.append(line.split())
 
for row in res:
    print(*row)

import random
f=open('int.txt','w')
m=6
n=7
a=[[random.randrange(-5,6) for j in range(n)] for i in range(m)]
str(a)
 
 
for i in range(len(a)):
    for j in range(len(a[i])):
        res="%-6d" %(a[i][j])
        f.write(res)
    f.write('\n')
f.close()

import random
 
 
def write_to_file(fn, m):
    with open(fn, 'w') as f:
        for row in m:
            f.write(' '.join(row)+'\n')
 
 
def read_from_file(fn):
    with open(fn) as f:
        return [line.split() for line in f]
 
 
random_matrix = [[str(random.randint(-10, 10)) for _ in range(6)] for _ in range(7)]
print('generated and written to file\n', random_matrix)
write_to_file('output.txt', random_matrix)
 
read_matrix = read_from_file('output.txt')
print('read from file\n', read_matrix)
 
changed_matrix = [[1 if int(num) >= 0 else 0 for num in line] for line in read_matrix]
print('changed to 1s and 0s\n', changed_matrix)

...
changed_matrix = [['1' if int(num) >= 0 else '0' for num in line] for line in read_matrix]
print('changed to 1s and 0s\n', changed_matrix)
write_to_file('output.txt', changed_matrix)