Here is a helpful little script that will try to uncompress all file geodatabases in a single folder. It should be noted that if a file geodatabase is already uncompressed, it will just be ignored.
from arcpy import env
if __name__ == '__main__':
workspace = arcpy.GetParameterAsText(0)
env.workspace = workspace
fgdbs = arcpy.ListWorkspaces("*","FileGDB")
for fgdb in fgdbs:
env.workspace = None
So what I have done is list all file geodatabases in a given workspace (folder), then I just use the standard UncompressFileGeodatabaseData_management(). When I'm done processing, I set my environmental workspace variable to None just to clean up some loose ends. I could delete the object like fgdbs, but since they are self contained within the function, those variables should not persist beyond the life of the function.