sage and nohup

edit

Does anyone understand why the code below, saved in the file input.txt, does not work when it is run with the command

nohup sage < input.txt > output.txt &

(Of course, I use * for the product but it does not appear properly here)?

import sage.combinat.lyndon_word as LW

from sage.combinat.words.shuffle_product import ShuffleProduct_w1w2 as SP

from sage.combinat.free_module import CombinatorialFreeModule as CFM

F=CFM(QQ, ['a','b'])

R.<a,b>=FreeAlgebra(QQ,2)

Module=CombinatorialFreeModule(F.base_ring(),R)

def TP_free_algebra(w1,w2):
  if type(w1)==Integer:
    if type(w2)==Integer:
      return w1*w2*tensor((Module.basis()[1],Module.basis()[1]))
    else:
      L2=list(w2)
      result=0
      for i in L2:
        result+=w1*i[0]*tensor((Module.basis()[1],Module.basis()[i[1]]))    
      return result
  else:
    if type(w2)==Integer:
      L1=list(w1)
      result=0
      for i in L1:
        result+=w2*i[0]*tensor((Module.basis()[i[1]],Module.basis()[1]))    
      return result
    else:
      L1=list(w1)
      L2=list(w2)
      result=0
      for i in L1:
        for j in L2:
          result+=i[0]*j[0]*tensor((Module.basis()[i[1]],Module.basis()[j[1]]))
      return result

TP_free_algebra(Word('a'),Word('b'))