Python: Maximum recursion depth exceeded

Question

I have the following recursion code, at each node I call sql query to get the nodes belong to the parent node.

here is the error:

Exception RuntimeError: 'maximum recursion depth exceeded' in <bound method DictCursor.__del__ of <MySQLdb.cursors.DictCursor object at 0x879768c>> ignored  RuntimeError: maximum recursion depth exceeded while calling a Python object Exception AttributeError: "'DictCursor' object has no attribute 'connection'" in <bound method DictCursor.__del__ of <MySQLdb.cursors.DictCursor object at 0x879776c>> ignored 

Method that I call to get sql results:

def returnCategoryQuery(query, variables={}):     cursor = db.cursor(cursors.DictCursor);     catResults = [];     try:         cursor.execute(query, variables);         for categoryRow in cursor.fetchall():             catResults.append(categoryRow['cl_to']);         return catResults;     except Exception, e:         traceback.print_exc(); 

I actually don't have any issue with the above method but I put it anyways to give proper overview of the question.

Recursion Code:

def leaves(first, path=[]):     if first:         for elem in first:             if elem.lower() != 'someString'.lower():                 if elem not in path:                     queryVariable = {'title': elem}                     for sublist in leaves(returnCategoryQuery(categoryQuery, variables=queryVariable)):                         path.append(sublist)                         yield sublist                     yield elem 

Calling the recursive function

for key, value in idTitleDictionary.iteritems():     for startCategory in value[0]:         print startCategory + " ==== Start Category";         categoryResults = [];         try:             categoryRow = "";             baseCategoryTree[startCategory] = [];             #print categoryQuery % {'title': startCategory};             cursor.execute(categoryQuery, {'title': startCategory});             done = False;             while not done:                 categoryRow = cursor.fetchone();                 if not categoryRow:                     done = True;                     continue;                 rowValue = categoryRow['cl_to'];                 categoryResults.append(rowValue);         except Exception, e:             traceback.print_exc();         try:             print "Printing depth " + str(depth);             baseCategoryTree[startCategory].append(leaves(categoryResults))         except Exception, e:             traceback.print_exc(); 

Code to print the dictionary,

print "---Printing-------" for key, value in baseCategoryTree.iteritems():     print key,     for elem in value[0]:         print elem + ',';     raw_input("Press Enter to continue...")     print 

If the recursion is too deep I should be getting the error when I call my recursion function, but when I get this error when I print the dictionary.

Answer 1

You can increment the stack depth allowed - with this, deeper recursive calls will be possible, like this:

import sys sys.setrecursionlimit(10000) # 10000 is an example, try with different values 

... But I'd advise you to first try to optimize your code, for instance, using iteration instead of recursion.