[Tutor] recursive problem

[Roelof Wobben]

From: anand.shashwat at gmail.com
Date: Thu, 9 Sep 2010 15:08:10 +0530
Subject: Re: [Tutor] recursive problem
To: rwobben at hotmail.com
CC: tutor at python.org




On Thu, Sep 9, 2010 at 2:21 PM, Roelof Wobben <rwobben at hotmail.com> wrote:


Hello, 
 
I have this :
 
def recursive_count(target, nested_num_list):
    """
      >>> recursive_count(2, [2, 9, [2, 1, 13, 2], 8, [2, 6]])
      4
      >>> recursive_count(7, [[9, [7, 1, 13, 2], 8], [7, 6]])
      2
      >>> recursive_count(15, [[9, [7, 1, 13, 2], 8], [2, 6]])
      0
      >>> recursive_count(5, [[5, [5, [1, 5], 5], 5], [5, 6]])
      6
    """
    for element in nested_num_list:
        if type(element) == type([]):
           test = recursive_count(target, element)
        print element, target
        if element == target :
           count = count + 1
    return count
 
if __name__ == "__main__":
    import doctest
    doctest.testmod()
 
 
Now I get this message :
 
UnboundLocalError: local variable 'count' referenced before assignment


It is because you are doing count = count + 1
But where is count defined.
 


 
But if I do this :
 
def recursive_count(target, nested_num_list):
    """
      >>> recursive_count(2, [2, 9, [2, 1, 13, 2], 8, [2, 6]])
      4
      >>> recursive_count(7, [[9, [7, 1, 13, 2], 8], [7, 6]])
      2
      >>> recursive_count(15, [[9, [7, 1, 13, 2], 8], [2, 6]])
      0
      >>> recursive_count(5, [[5, [5, [1, 5], 5], 5], [5, 6]])
      6
    """
  count = 0 
  for element in nested_num_list:
        if type(element) == type([]):
           test = recursive_count(target, element)
        print element, target
        if element == target :
           count = count + 1
    return count
 
if __name__ == "__main__":
    import doctest
    doctest.testmod()
 
The count will always be 0 if a nested list is being found.
 
What's the python way to solve this 


I am not sure what do you want to achieve by this ?
What is the problem statement ?
 
The problem statement is that I must count how many times the target is in the nested_list.
So I thougt that every nested list the function is called again so this list is also iterated.
 
Roelof
  		 	   		  
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