Python Code Generator

[MTVDNA]

I would use a dictionary, and make use of the modulo operator. Something like this:

N_cols = 30
name2index = {"{}{}".format(chr(65 + int(a/12)), a%12 + 1):(a+1) for a in range(N_cols)}
print(name2index)

print(name2index['A1'])
print(name2index['B12'])

int(a/12) turns a number into an integer, dropping any decimals. So int(1/12) = 0, int(2/12) = 0, ..., int(12/12) = 1, int(13/12) = 1, etc. We can use this to get the letter.
The modulo operator % gives the remainder of a certain division. So 0 % 12 = 0, 1 % 12 = 1, 2 % 12 = 2, ... , 12 % 12 = 0, 13 % 12 = 1, 14 % 12 = 2, etc.

The outermost braces {} turn it into a dictionary. The keys are 'A1', 'A2', etc. and the values are 1, 2, 3, 4...

P.S. here's my version for replicating tests

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def transfer(p_amount, p_source, p_target):
 print("Transfering {:>4}ul from {} to {}".format(p_amount, p_source, p_target))


# nr of mastermixes
N_mm = 3
# nr of cDNA samples
N_cDNA = 3
# nr of tests to run on each sample
N_tests = 2

mastermix_sources = list("A{}".format(j) for j in range(N_mm))
cDNA_sources = list("B{}".format(j) for j in range(N_cDNA))

print("{:<20}{}".format("mastermix sources", mastermix_sources))
print("{:<20}{}".format("cDNA sources", cDNA_sources))


for i, mm in enumerate(mastermix_sources):
  #list of targets for mastermix
  targets = []
  
  for j in range(N_cDNA * N_tests):
    column = chr(65+i)
    row = j+1
    target = "{}{}".format(column, row)
    targets.append(target)
  
  transfer(
           6, 
           mm,
           targets
         )


for i, cd in enumerate(cDNA_sources):
  
  #list of targets for cDNA
  targets = []
  
  # loop over the nr of mastermixes
  for j in range(N_mm):
    # then loop over the nr of tests
    for k in range(N_tests):
      column = chr(65 + j)
      row = 1 + k + i*N_tests 
      target = "{}{}".format(column, row)
      targets.append(target)
  
  transfer(
             4, 
             cd,
             targets
           )

Which gives me

Output:
mastermix sources   ['A0', 'A1', 'A2']
cDNA sources        ['B0', 'B1', 'B2']
Transfering    6ul from A0 to ['A1', 'A2', 'A3', 'A4', 'A5', 'A6']
Transfering    6ul from A1 to ['B1', 'B2', 'B3', 'B4', 'B5', 'B6']
Transfering    6ul from A2 to ['C1', 'C2', 'C3', 'C4', 'C5', 'C6']
Transfering    4ul from B0 to ['A1', 'A2', 'B1', 'B2', 'C1', 'C2']
Transfering    4ul from B1 to ['A3', 'A4', 'B3', 'B4', 'C3', 'C4']
Transfering    4ul from B2 to ['A5', 'A6', 'B5', 'B6', 'C5', 'C6']