小编Jor*_*ack的帖子

我有以下代码失败,出现以下错误:

RuntimeError:超出最大递归深度

我试图重写它以允许尾递归优化(TCO).我相信如果发生TCO,这段代码应该是成功的.

def trisum(n, csum):
    if n == 0:
        return csum
    else:
        return trisum(n - 1, csum + n)

print(trisum(1000, 0))

我是否应该断定Python不执行任何类型的TCO,或者我只是需要以不同的方式定义它？

我正在尝试查询DynamoDB表以查找email未设置该属性的所有项目.EmailPasswordIndex表中存在一个全局二级索引,包括该email字段.

var params = {
    "TableName": "Accounts",
    "IndexName": "EmailPasswordIndex",
    "KeyConditionExpression": "email = NULL",
};

dynamodb.query(params, function(err, data) {
    if (err)
        console.log(JSON.stringify(err, null, 2));
    else
        console.log(JSON.stringify(data, null, 2));
});

结果:

{
  "message": "Invalid KeyConditionExpression: Attribute name is a reserved keyword; reserved keyword: NULL",
  "code": "ValidationException",
  "time": "2015-12-18T05:33:00.356Z",
  "statusCode": 400,
  "retryable": false
}

表定义:

var params = {
    "TableName": "Accounts",
    "KeySchema": [
        { "AttributeName": "id", KeyType: "HASH" }, // Randomly generated UUID
    ],
    "AttributeDefinitions": [
        { …

我正在寻找Chrome中渲染错误的解决方法.当select元素具有大约90%+隐藏选项元素时,它会显示出来.在Chrome中,下拉高度太短而无法使用.这似乎不会发生在其他浏览器上.查看jsFiddle上的示例.

HTML Example
Note: Some options were removed to keep the code brief.
The bug does not show up unless all options are present.

100 Options, 90% Hidden:<br>
<select>
<option value="">Select an Option</option>
<option value="0" style="display: none">Option 0</option>
<option value="1" style="display: none">Option 1</option>
<option value="2" style="display: none">Option 2</option>
<option value="3" style="display: none">Option 3</option>
<!-- Options removed for brevity. -->
<option value="86" style="display: none">Option 86</option>
<option value="87" style="display: none">Option 87</option>
<option value="88" style="display: none">Option 88</option>
<option value="89" style="display: none">Option 89</option> …

您的应用程序在后台完成其操作后取则必须调用completionHandler块与三一点UIBackgroundFetchResult的状态:UIBackgroundFetchResultNoData,UIBackgroundFetchResultNewData或UIBackgroundFetchResultFailed.

一旦调用完成处理程序,操作系统如何处理这三个结果中的每一个？