我的收藏看起来像这样.
{
"_id" : ObjectId("572c4ed33c1b5f51215219a8"),
"name" : "This is an angular course, and integeration with php",
"description" : "After we connected we can query or update the database just how we would using the mongo API with the exception that we use a callback. The format for callbacks is always callback(error, value) where error is null if no exception has occured. The update methods save, remove, update and findAndModify also pass the lastErrorObject as the last argument to the callback …我有熊猫数据框网址
location dom_category
3 'edu'
3 'gov'
3 'edu'
4 'org'
4 'others'
4 'org'
我希望这个数据框像
location edu gov org others
3 2 1 0 0
4 0 0 2 1
edu、gov、org 和其他包含特定位置的计数。我有正确的代码，但我知道它不是优化的
url['val']=1
url_final=url.pivot_table(index=['location'],values='val',columns=
['dom_category'],aggfunc=np.sum)
我的文件看起来像这样。
{
"_id" : ObjectId("572c4bffd073dd581edae045"),
"name" : "What's New in PHP 7",
"description" : "PHP 7 is the first new major version number of PHP since 2004. This course shows what's new, and what's changed.",
"difficulty_level" : "Beginner",
"type" : "Normal",
"tagged_skills" : [
{
"_id" : "5714e894e09a0f7d804b2254",
"name" : "PHP"
}
],
"created_at" : 1462520831.649,
"updated_at" : 1468233074.243 }
是否可以在单个查询中获取最近的 5 个文档和总数。我对这个要求使用了两个查询，如下所示。
db.course.find().sort({created_at:-1}).limit(5)
db.course.count()