01/01/1981/;42.989
02/01/1981/;32.093
03/01/1981/;25.334
04/01/1981/;25.334
05/01/1981/;25.767
06/01/1981/;28.868
07/01/1981/;40.925
08/01/1981/;29.777
...
04/02/1981/;27.969
05/02/1981/;27.969
06/02/1981/;29.777
07/02/1981/;30.696
...
29/12/2014/;91.843
30/12/2014/;83.645
31/12/2014/;77.336

for row in arq:
    a = row.split(';')
    x = a[0]
    y = float(a[1])
    x = row.split("/" or "/;  ")
    day = int(x[0])
    month = int(x[1])
    year = int(x[2])
    nl.append(y)
    average = sum(nl)/ len(nl)
print(average)