This is possible by using rb-mergeplays by lachlan. To give your loved songs on Last.fm five stars (in rating) in Rhythmbox do as follows:

• Download lastexport.py and rate5loved.py



• Then do as the README says:

  
  
  

  
  

  
  

  • Pull your loved tracks with lastexport:

    
    
    

    python ./lastexport.py -u your_lastfm_username -t loved -o loved.txt
    
    

  
  

  • Merge with database:

    
    
    

    python ./rate5loved.py loved.txt
    
    

  
  

  
  

  
  
  

  Note that you need to replace your_lastfm_username with your Last.fm user name. Also note that you need to cd to the directory where the scripts are before you execute them.