Python:超过最大递归深度 [英] Python: Maximum recursion depth exceeded

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问题描述

我有以下递归代码,在每个节点上我都调用sql查询以获取属于父节点的节点.

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

这是错误:

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

我调用以获得sql结果的方法:

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();

我实际上对上述方法没有任何问题,但是我还是把它放在了问题的正确位置上.

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

递归代码:

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

调用递归函数

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();

用于打印字典的代码

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

如果递归太深,则在调用递归函数时会出现错误,但是在打印字典时出现此错误.

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.

推荐答案

您可以增加允许的堆栈深度-这样,将可以进行更深层次的递归调用,如下所示:

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

...但是我建议您首先尝试优化代码,例如,使用迭代而不是递归.

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

这篇关于Python:超过最大递归深度的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!

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