generate permutation using recursion | how to

Here is a Python program to generate all permutations using recursion. I just wrote the code while preparing for a class in national programming camp. If you study it carefully, you will have some idea about backtracking.

 
 taken = []  
 
 def process(X):  
      print X  
 
 def recurse(li, X, i, n):  
      if i == n:  
           process(X[0:i])  
      else:  
           for j in range(0, n):  
                if taken[j] == False:  
                     taken[j] = True  
                     X.append(li[j])  
                     recurse(li, X, i+1, n)  
                     taken[j] = False  
                     X.pop(i)  
 
 if __name__ == "__main__":  
      li = [1, 2, 3, 4]  
      X = []  
      taken.extend([False, False, False, False])  
      print taken  
      recurse(li, X, 0, li.__len__())