Nia_proggie | Python Fiddle

def gen_plate_layout(cols):
    
  pp=[]

for col in range(1, cols + 1):
    for row in ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H']:
      pp.append(row + str(col))
   
  return pp

PLATE_POSITIONS = gen_plate_layout(12)

your_list = ['h3', 'a4', 'b4', 'c4', 'd4', 'e4', 'f4', 'g4', 'h4', 'a5']
#your_list = ['B3', 'C1', 'G3', 'B2']

def plate_target(well):
  targets_base = [0, 8, 16, 24, 32, 40]
    
  well_index = PLATE_POSITIONS.index(well)
  well_col = well_index/8
  well_row = well_index % 8
 
  plate = well_col/2 + 1
    
  if (well_col - 1) % 2:      #odd columns (ie w/ even column indexes)
    targets_indexes = [x + well_row for x in targets_base]
  else:
    targets_indexes = [48 + x + well_row for x in targets_base]

#print targets_indexes
    
  return {'plate': plate,
          'target': [PLATE_POSITIONS[index] for index in targets_indexes]
          }

your_list = [i.upper() for i in your_list]

plates_and_targets = map(plate_target, your_list)
print plates_and_targets

print "===================="

plates = []
for p in [1,2,3]:
  print "Plate " + str(p)
  for t in [d['target'] for d in plates_and_targets if d['plate'] == p]:
    print t
  print ""

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