CODEWITHSUNDEEP
pythongoogle-app-enginesettings
hoju
hoju

Reputation: 29452

storing app settings on Google App Engine

I need to store settings for my Google App Engine project. Currently I have:

class Settings(db.Model):
    rate = db.IntegerProperty(default=4)
    ...

And when I want to use it:

Settings.get_or_insert('settings')

This feels clumsy so is there a better way (without using Django)?

Upvotes: 5

Views: 565

Answers (2)

Martin Omander
Martin Omander

Reputation: 3604

In my projects, I put config data in the datastore (one record per config value) using this class:

from google.appengine.ext import ndb

class Settings(ndb.Model):
  name = ndb.StringProperty()
  value = ndb.StringProperty()

  @staticmethod
  def get(name):
    NOT_SET_VALUE = "NOT SET"
    retval = Settings.query(Settings.name == name).get()
    if not retval:
      retval = Settings()
      retval.name = name
      retval.value = NOT_SET_VALUE
      retval.put()
    if retval.value == NOT_SET_VALUE:
      raise Exception(('Setting %s not found in the database. A placeholder ' +
        'record has been created. Go to the Developers Console for your app ' +
        'in App Engine, look up the Settings record with name=%s and enter ' +
        'its value in that record\'s value field.') % (name, name))
    return retval.value

Your application would do this to get a value:

API_KEY = Settings.get('API_KEY')

If there is a value for that key in the datastore, you will get it. If there isn't, a placeholder record will be created and an exception will be thrown. The exception will remind you to go to the Developers Console and update the placeholder record.

I find this takes the guessing out of setting config values. If you are unsure of what config values to set, just run the code and it will tell you!

Upvotes: 0

Alex Martelli
Alex Martelli

Reputation: 881555

Please clarify what does "feel clumsy" to you about this -- that's not very clear to me.

The datastore is the way to persist updatable data in App Engine (blobstore's for huge blobs, memcache's not guaranteed persistent). If your settings can't be changed by the application of course you can just put them in your own custom .yaml file (or whatever, but yaml's how App Engine's own configuration files are already stored anyway...;-); just remember all such files are read-only from the application's viewpoint. YAML is conveniently available to App Engine apps for parsing their own .yaml (but "read-only") files.

Upvotes: 4

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