title: python list of dictionaries group by and filter issue
body: <p>I have the following list of dictionaries. The list is already sorted. Now I have to group by worker and get his "prskill", but if in case there is not other option he gets None.</p>
  
  <p>For each worker there are max two dictionaries, one with "prskill" None and one with the actual value. if there is only one dictionary his "prskill" is None</p>
  
  <p>my list</p>
  
  <pre><code>sorted =    [{worker_nick:  1B  prskill:  None },
  {worker_nick:  B1  prskill:  None },
  {worker_nick:  B2  prskill:  None },
  {worker_nick:  Božić  prskill:  None },
  {worker_nick:  Božić  prskill:  Bolničar },
  {worker_nick:  Cimermančič  prskill:  None },
  {worker_nick:  Cimermančič  prskill:  Bolničar },
  {worker_nick:  CindrićJ  prskill:  None },
  {worker_nick:  CindrićJ  prskill:  razno },
  {worker_nick:  CipurićA  prskill:  None },
  {worker_nick:  CipurićA  prskill:  Strežnik },
  {worker_nick:  Dančulović  prskill:  None },
  {worker_nick:  Dančulović  prskill:  Strežnik },
  {worker_nick:  Dragovan  prskill:  Bolničar },
  {worker_nick:  Dragovan  prskill:  None },
  {worker_nick:  Fofana  prskill:  SestraOdd },
  {worker_nick:  Fofana  prskill:  None },
  {worker_nick:  GovednikM  prskill:  None },
  {worker_nick:  GovednikM  prskill:  Strežnik },
  {worker_nick:  Hoenigman  prskill:  None },
  {worker_nick:  Hoenigman  prskill:  SestraOdd },
  {worker_nick:  Husič  prskill:  None },
  {worker_nick:  Huskić  prskill:  Bolničar },
  {worker_nick:  Huskić  prskill:  None },
  {worker_nick:  JD-Šuligoj  prskill:  JD },
  {worker_nick:  JD-Šuligoj  prskill:  None },
  {worker_nick:  Jakša  prskill:  Gospodinja },
  {worker_nick:  Jakša  prskill:  None },
  {worker_nick:  Kastelic  prskill:  SestraOdd },
  {worker_nick:  Kastelic  prskill:  None },
  {worker_nick:  Lukinić  prskill:  SestraOdd },
  {worker_nick:  Lukinić  prskill:  None },
  {worker_nick:  MaceleJ  prskill:  None },
  {worker_nick:  MaceleJ  prskill:  Bolničar },
  {worker_nick:  MaceleM  prskill:  SestraAmb },
  {worker_nick:  MaceleM  prskill:  None },
  {worker_nick:  Miketič  prskill:  Bolničar },
  {worker_nick:  Miketič  prskill:  None },
  {worker_nick:  MikešićG  prskill:  SestraOdd },
  {worker_nick:  MikešićG  prskill:  None },
  {worker_nick:  Muc  prskill:  None },
  {worker_nick:  Muc  prskill:  Bolničar },
  {worker_nick:  Petraš  prskill:  None },
  {worker_nick:  Petraš  prskill:  Terapevt },
  {worker_nick:  Pezdirc  prskill:  SestraOdd },
  {worker_nick:  Pezdirc  prskill:  None },
  {worker_nick:  Prevalšek  prskill:  Bolničar },
  {worker_nick:  Prevalšek  prskill:  None },
  {worker_nick:  Ramušćak  prskill:  SestraAmb },
  {worker_nick:  Ramušćak  prskill:  None },
  {worker_nick:  S-T1  prskill:  None },
  {worker_nick:  S-T2  prskill:  None },
  {worker_nick:  S1  prskill:  None },
  {worker_nick:  Slanc  prskill:  Terapevt },
  {worker_nick:  Slanc  prskill:  None },
  {worker_nick:  Sneljer  prskill:  Terapevt },
  {worker_nick:  Sneljer  prskill:  None },
  {worker_nick:  Stepan  prskill:  SestraOdd },
  {worker_nick:  Stepan  prskill:  None },
  {worker_nick:  Sudac  prskill:  None },
  {worker_nick:  Sudac  prskill:  Bolničar },
  {worker_nick:  Tkalac  prskill:  Bolničar },
  {worker_nick:  Tkalac  prskill:  None },
  {worker_nick:  Vidovič  prskill:  SestraOdd },
  {worker_nick:  Vidovič  prskill:  None },
  {worker_nick:  VukšiničM  prskill:  None },
  {worker_nick:  VukšiničM  prskill:  Bolničar },
  {worker_nick:  Vučič  prskill:  Bolničar },
  {worker_nick:  Vučič  prskill:  None },
  {worker_nick:  Čurči  prskill:  None },
  {worker_nick:  Čurči  prskill:  Bolničar },
  {worker_nick:  Šterk  prskill:  None },
  {worker_nick:  Šterk  prskill:  Namestnik direktorja }]
  </code></pre>
  
  <p>Any suggestions?</p>
  
  <p>Thank you</p>