Заполнение массива по спирали

def print_pretty(a):
    for row in a:
        print(''.join(list(map(lambda x: ' '*(4- len(str(x)))+str(x), row))))
 
strings = input().split()
n = int(strings[0])
m = int(strings[1])
left = 0
right = 0
top = 0
is_first = True
bottom = 0
counter = 0
string = 'l-r'
a = [[0] * m for i in range(n)]
 
for k in range(n * m):
    if n == 1 and m == 1:
        a[0][0] = 1
        break
    if (left + right + counter == m - 1) and (string == 'l-r'):
        string = 't-b'
        counter = 0
        top += 1
        is_first = False
    if (bottom + top + counter == n) and (string == 't-b'):
        string = 'r-l'
        counter = 0
        right += 1
    if (left + right + counter == m) and (string == 'r-l'):
        string = 'b-t'
        counter = 0
        bottom += 1
    if (left + right + counter == n) and (string == 'b-t'):
        string = 'l-r'
        counter = 0
        left += 1
 
    if is_first:
        a[top][counter + left] = k + 1
    if string == 'l-r':
        a[top][counter + left] = k + 1
    if string == 't-b':
        a[counter + top - 1][m - right - 1] = k + 1
    if string == 'r-l':
        a[n - bottom - 1][m - counter - right] = k + 1
    if string == 'b-t':
        a[n - bottom - counter][left] = k + 1
    counter += 1
 
print_pretty(a)

def print_pretty(a):
    for row in a:
        print(''.join(list(map(lambda x: ' ' * (4 - len(str(x))) + str(x), row))))
 
 
n, m = list(map(int, input().split()))
left = 0
right = 0
top = 0
is_first = True
bottom = 0
counter = 0
string = 'l-r'
a = [[0] * m for i in range(n)]
 
for k in range(n * m):
    if n == 1 and m == 1:
        a[0][0] = 1
        break
    elif (left + right + counter >= m - 1) and (string == 'l-r'):
        if left + right + counter > m - 1:
            counter = 1
        else:
            counter = 0
        string = 't-b'
        top += 1
        is_first = False
    elif (bottom + top + counter == n) and (string == 't-b'):
        string = 'r-l'
        counter = 0
        right += 1
    elif (left + right + counter == m) and (string == 'r-l'):
        string = 'b-t'
        counter = 0
        bottom += 1
    elif (left + right + counter == n) and (string == 'b-t'):
        string = 'l-r'
        counter = 0
        left += 1
 
    if is_first:
        a[top][counter + left] = k + 1
    elif string == 'l-r':
        a[top][counter + left] = k + 1
    elif string == 't-b':
        a[counter + top - 1][m - right - 1] = k + 1
    elif string == 'r-l':
        a[n - bottom - 1][m - counter - right] = k + 1
    elif string == 'b-t':
        a[n - bottom - counter][left] = k + 1
    counter += 1
 
print_pretty(a)