to sum a list in a dictonary

[Beema shafreen]

hi everybody,
               I need to sum a list in dictionary...
my script,
       d = {}
probes = list(enumerate((i.split('\t')[2],i.split('\t')[3],
i.split('\t')[4])for
i in open('final_lenght_probe_span')))
for idx, (probe_id, span, length) in probes:
         try :
                l = [span,length.strip(),probes[idx+1][1][1]]
                d[probe_id] = sum[l]

         except IndexError :
                none = 0
                l = [span,length,None]
                d[probe_id] = sum[l]
for key in d.keys():
        print key, d[key]


I used an built-in fuction sum to add the list, but is results in error...
now how do i do it

my file used is:
  2709852         2709911       A_16_P21360207  405     -59
  2710316         2710367       A_14_P136880    -42     -51
  2710325         2710384       A_16_P21360209  876     -59
  2711260         2711319       A_16_P21360210  -22     -59
  2711297         2711356       A_16_P03641959  254     -59
  2711610         2711659       A_16_P03641960  982     -49
  2712641         2712696       A_16_P03641962  1011    -55
  2713707         2713765       A_16_P41563648  43      -58
  2713808         2713861       A_16_P03641963  -16     -53
  2713845         2713893       A_16_P41563649  3460    -48
  2717353         2717412       A_16_P03641964  214     -59
  2717626         2717685       A_16_P41563655  25      -59
  2717710         2717754       A_16_P03641965  1250    -44
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