My code works for a single list but not for a nest

Question

I have an assignment to do. I found out how to execute what is required in my own way but the solution is only partial. It doesn't work for a nested list. These are my codes.

    def calc_averages():

    allprices =[  ['', '',  '',  '', 1.0, 2.0, 1.2, 1.3, 1.1,  '',  '',  ''],
       ['',  '',  '', 1.2, 1.0, 2.0, 1.2, 1.3, 1.1,  '',  '',  ''],
       ['',  '',  '', 1.2,  '', 1.8, 1.3, 1.1,  '',  '', '',  ''],
       ['',  '',  '',  '', 1.0, 2.0, 1.2, 1.2,  '',  '',  '',  ''],
       ['',  '',  '',  '', 1.0, 2.0, 1.1, 1.2, 1.4, 1.8, 1.9, 2.2]    ]

    averages = []
    aList = []

    for lst in allprices:
        aList.append(lst[5])

    averages.append(sum(aList)/len(aList))

    return averages

This works fine for calculating the average of a single month which is the total of 6th value from each list divided by 5. However, when I try to calculate the average for all 12 months using the above code, it doesn't work unless I change those empty strings to 0s.

    ef calc_averages():

allprices =[  [0,  0,  0,  0, 1.0, 2.0, 1.2, 1.3, 1.1,  0,  0,  0],
       [0,  0,  0, 1.2, 1.0, 2.0, 1.2, 1.3, 1.1,  0,  0,  0],
       [0,  0,  0, 1.2,  0, 1.8, 1.3, 1.1,  0,  0, 0,  0],
       [0,  0,  0,  0, 1.0, 2.0, 1.2, 1.2,  0,  0,  0,  0],
       [0,  0,  0,  0, 1.0, 2.0, 1.1, 1.2, 1.4, 1.8, 1.9, 2.2]    ]


averages = []
aList = []
bList = []
cList = []
dList = []
eList = []
fList = []
gList = []
hList = []
iList = []
jList = []
kList = []
lList = []

for lst in allprices:
    aList.append(lst[0])
    bList.append(lst[1])
    cList.append(lst[2])
    dList.append(lst[3])
    eList.append(lst[4])
    fList.append(lst[5])
    gList.append(lst[6])
    hList.append(lst[7])
    iList.append(lst[8])
    jList.append(lst[9])
    kList.append(lst[10])
    lList.append(lst[11])


averages.append(sum(aList)/len(aList))
averages.append(sum(bList)/len(bList))
averages.append(sum(cList)/len(cList))
averages.append(sum(dList)/len(dList))
averages.append(sum(eList)/len(eList))
averages.append(sum(fList)/len(fList))
averages.append(sum(gList)/len(gList))
averages.append(sum(hList)/len(hList))
averages.append(sum(iList)/len(iList))
averages.append(sum(jList)/len(jList))
averages.append(sum(kList)/len(kList))
averages.append(sum(lList)/len(lList))

return averages

When I try to run it with those empty strings, it gives me this error; TypeError: unsupported operand type(s) for +: 'int' and 'str'

I am also aware that it is not written in a good way. If you have any suggestions for improvement please tell me. Thank you already :)

Answer 1

Your issue is that you are trying to add a string and an int together.

Instead of sum(aList)/len(aList), I would do

sum(list(filter(lambda x: x != '', aList)))/ len(aList) 

which removes all the empty characters out from the list.

To wrap everything together where I clean up you having multiple lists:

def main():
    allprices =[['', '',  '',  '', 1.0, 2.0, 1.2, 1.3, 1.1,  '',  '',  ''],
       ['',  '',  '', 1.2, 1.0, 2.0, 1.2, 1.3, 1.1,  '',  '',  ''],
       ['',  '',  '', 1.2,  '', 1.8, 1.3, 1.1,  '',  '', '',  ''],
       ['',  '',  '',  '', 1.0, 2.0, 1.2, 1.2,  '',  '',  '',  ''],
       ['',  '',  '',  '', 1.0, 2.0, 1.1, 1.2, 1.4, 1.8, 1.9, 2.2]]

    alllists = [[allprices[i][j] for i in range(len(allprices))] for j in range(12)]
    averages = []
    for alist in alllists:
        averages.append(sum(list(filter(lambda x: x != '', alist)))/ len(alist))

    print(averages)
main()