Helper for performing operations on matrix elements

linalg.py

print('enter row count:');
row_count = int(input());

print('enter col count:');
col_count = int(input());

print(f'creating matrix size %dx%d' % (col_count, row_count));

m = [];
for i in range(row_count):
  l = [];
  m.append(l);
  for j in range(col_count):
    l.append(0);


def print_matrix(m):
  for i in range(len(m)):
    for j in range(len(m[i])):
      print(f'% 5.5f\t' % m[i][j], end=' ');
    print('');

row_index = 0;
while True:
  print(f'enter row #%d (separate by spaces):' % (1+row_index));
  row_input = input().split(' ');
  val_count = len(row_input);
  if val_count != col_count:
    print(f'number of inputs (%d) doesnt match column count.' % val_count);
    continue;
  for val_index in range(len(row_input)):
    input_string = row_input[val_index];
    m[row_index][val_index] = float(input_string);
  row_index += 1;
  if row_index == row_count:
    break;

print('your matrix:');
print_matrix(m);

while True:
  print('chose what to do: (h for help)');
  op = input();
  if op.startswith('h'):
    print('h            - print help');
    print('m r n        - multiply r by number n, store in r');
    print('d r n        - divide r by number n, store in r');
    print('a r1 r2 ?[m] - add r2 multiplied by m (def.=1) to r1 and store in r1');
    print('s r1 r2      - swap r1 and r2');
  elif op.startswith('m'):
    args = op.split(' ');
    if len(args) != 3:
       print('expected 3 arguments (h for help)');
       continue;
    row = int(args[1])-1;
    mul = float(args[2]);
    for i in range(col_count):
      m[row][i] = m[row][i] * mul;
    print_matrix(m);
  elif op.startswith('d'):
    args = op.split(' ');
    if len(args) != 3:
       print('expected 3 arguments (h for help)');
       continue;
    row = int(args[1])-1;
    div = float(args[2]);
    for i in range(col_count):
      m[row][i] = m[row][i] / div	;
    print_matrix(m);
  elif op.startswith('a'):
    args = op.split(' ');
    if len(args) < 3 or len(args) > 4:
      print('expected 2 or 3 args (h for help)');
      continue;
    r1 = int(args[1])-1;
    r2 = int(args[2])-1;
    mul = 1;
    if len(args) == 4:
      mul = float(args[3]);
    for i in range(col_count):
      m[r1][i] = m[r1][i] + m[r2][i] * mul;
    print_matrix(m);
  elif op.startswith('s'):
    args = op.split(' ');
    if len(args) != 3:
      print('expected 2 args (h for help)');
      continue;
    r1 = int(args[1])-1;
    r2 = int(args[2])-1;
    t = m[r1];
    m[r1] = m[r2];
    m[r2] = t;
    print_matrix(m);
  elif op.startswith('q'):
    break;