Module Registry

The Blender.Registry submodule.

Registry

This module provides a way to create, retrieve and edit persistent data in Blender.

When a script is executed it has its own private global dictionary, which is deleted when the script exits. This is done to avoid problems with name clashes and garbage collecting. But because of this, the data created by a script isn't kept after it leaves: the data is not persistent. The Registry module was created to give programmers a way around this limitation.

• saving arbitrary data from a script that itself or another one will need to access later.
• saving configuration data for a script: users can view and edit this data using the "Scripts Configuration Editor" script.
• saving the current state of a script's GUI (its button values) to restore it when the script is executed again.

 import Blender
 from Blender import Registry

 # this function updates the Registry when we need to:
 def update_Registry():
   d = {}
   d['myvar1'] = myvar1
   d['myvar2'] = myvar2
   d['mystr'] = mystr
   # cache = True: data is also saved to a file
   Blender.Registry.SetKey('MyScript', d, True)

 # first declare global variables that should go to the Registry:
 myvar1 = 0
 myvar2 = 3.2
 mystr = "hello"

 # then check if they are already there (saved on a
 # previous execution of this script):
 rdict = Registry.GetKey('MyScript', True) # True to check on disk also
 if rdict: # if found, get the values saved there
   try:
     myvar1 = rdict['myvar1']
     myvar2 = rdict['myvar2']
     mystr = rdict['mystr']
   except: update_Registry() # if data isn't valid rewrite it

 # ...
 # here goes the main part of the script ...
 # ...

 # if at some point the data is changed, we update the Registry:
 update_Registry()

Notes:

• In Python terms, the Registry holds a dictionary of dictionaries. Technically any Python or BPython object can be stored: there are no restrictions, but ...

• We have a few recommendations:

  Data saved to the Registry is kept in memory, so if you decide to store large amounts your script users should be clearly informed about it -- always keep in mind that you have no idea about their resources and the applications they are running at a given time (unless you are the only user), so let them decide.

  There are restrictions to the data that gets automatically saved to disk by SetKey(keyname, dict, True): this feature is only meant for simple data (bools, ints, floats, strings and dictionaries or sequences of these types). Strings are clamped if longer than 300 characters and at most 60 elements are allowed. Since this is only meant for scripts configuration variables, these are sensible restrictions, generous enough for the task.

  For more demanding needs, it's of course trivial to save data to another file or to a Blender Text.