如何检查实体是否存在于 gae 数据存储中?
How to check if entity exist in gae datastore?
我需要检查数据存储是否存在实体种类 "Kayit" 以创建新的 .
我的 db.model class:
class Kayit(db.Model):
url=db.StringProperty()
date = db.DateTimeProperty(auto_now_add=True)
目前正在使用它来检查,但它看起来并不优雅
class MainPage(webapp2.RequestHandler):
def get(self):
r_name="none"
q=db.Query(Kayit)
try:
self.response.write(q[0].url)
except:
kay=Kayit(parent=_DefterKey(r_name),key_name='alibaba')
kay.url="some url"
kay.put()
我猜我们用 db.Key.from_path('Kayit', 1) 得到了父键。我如何使用它来检查它是否有实体?
回答者:
How to query parent entity from child entity in Google App Engine (Python) NDB/Datastore?
记录在云端 API:
https://cloud.google.com/appengine/docs/java/javadoc/com/google/appengine/api/datastore/Entity
...并显示在 python "Guestbook" google 示例中:
https://cloud.google.com/appengine/docs/python/gettingstartedpython27/usingdatastore
看看下面的节:
greetings_query = Greeting.query(
ancestor=guestbook_key(guestbook_name)).order(-Greeting.date)
greetings = greetings_query.fetch(10)
我需要检查数据存储是否存在实体种类 "Kayit" 以创建新的 . 我的 db.model class:
class Kayit(db.Model):
url=db.StringProperty()
date = db.DateTimeProperty(auto_now_add=True)
目前正在使用它来检查,但它看起来并不优雅
class MainPage(webapp2.RequestHandler):
def get(self):
r_name="none"
q=db.Query(Kayit)
try:
self.response.write(q[0].url)
except:
kay=Kayit(parent=_DefterKey(r_name),key_name='alibaba')
kay.url="some url"
kay.put()
我猜我们用 db.Key.from_path('Kayit', 1) 得到了父键。我如何使用它来检查它是否有实体?
回答者:
How to query parent entity from child entity in Google App Engine (Python) NDB/Datastore?
记录在云端 API:
https://cloud.google.com/appengine/docs/java/javadoc/com/google/appengine/api/datastore/Entity
...并显示在 python "Guestbook" google 示例中:
https://cloud.google.com/appengine/docs/python/gettingstartedpython27/usingdatastore
看看下面的节:
greetings_query = Greeting.query(
ancestor=guestbook_key(guestbook_name)).order(-Greeting.date)
greetings = greetings_query.fetch(10)