Using Python 3: I have 2 lists. One has many lists(each list has a letter and a

Question

Using Python 3:

I have 2 lists.

One has many lists(each list has a letter and a number) [ assume 1000 +].

One has letters [assume 100 + letters].

Listofcombo = [[‘a’, 2], [‘a’, 4], [‘b’, 2], [‘b’, 5], [‘c’, 12], [‘b’, 6], [‘c’, 5], ['d', 12], ............]

Listofletter = [‘a’, ‘b’, ‘c’, 'd', ........]

I want to sum the numbers from the same letters.

such as : 'a' = 2 + 4 + .......... = suma

'b' = 2 + 5 + 6 + ......... = sumb

'c' = 12 + 5 + ......... = sumc

'd' = 12 + ...... = sumd

.

.

.

.

Output will be:

Outputlist = [['a', suma], ['b', sumb], ['c', sumc], ['d', sumd], ..........]

I know should use for loops. But I do not know where to start w/.

Need helps!

Explanation / Answer

Python 3 code:

Listofcombo = [['a', 2], ['a', 4], ['b', 2], ['b', 5], ['c', 12], ['b', 6], ['c', 5], ['d', 12]]; # initialise Listofcombo
Listofletter = ['a', 'b', 'c', 'd']; #initialise Listofletter
mydictionary = {}
for i in range(0,len(Listofcombo)):
   if(Listofcombo[i][0] in mydictionary):
       mydictionary[Listofcombo[i][0]] = mydictionary[Listofcombo[i][0]] + Listofcombo[i][1]
   else:
       mydictionary[Listofcombo[i][0]] = Listofcombo[i][1]      
outputlist = []
for key in mydictionary:
   tmp = []
   tmp.append(key)
   tmp.append(mydictionary[key])
   outputlist.append(tmp)
print(outputlist)

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