def ToReducedRowEchelonForm( M):
    if not M: return
    lead = 0
    rowCount = len(M)
    columnCount = len(M[0])
    for r in range(rowCount):
        if lead >= columnCount:
            return
        i = r
        while M[i][lead] == 0:
            i += 1
            if i == rowCount:
                i = r
                lead += 1
                if columnCount == lead:
                    return
        M[i],M[r] = M[r],M[i]
        lv = M[r][lead]
        M[r] = [ mrx / float(lv) for mrx in M[r]]
        for i in range(rowCount):
            if i != r:
                lv = M[i][lead]
                M[i] = [ iv - lv*rv for rv,iv in zip(M[r],M[i])]
        lead += 1


mtx = [
   [ 1, 2, -1, -4],
   [ 2, 3, -1, -11],
   [-2, 0, -3, 22],]

ToReducedRowEchelonForm( mtx )

for rw in mtx:
  print ', '.join( (str(rv) for rv in rw) )