so the question is : average grade(grade list) return the average grade of all of the students in the list of lists grade list, where the inner lists contain a student ID and a grade.
this is what I have so far... but I don't know how to get the 2nd number for each list to get the average :/
grade_list=[['001',20],['002',45],['003',56]]
for i in grade_list:
i= sum(i)/3
print (i)
you can try, list comprehension
grade_list=[['001',20],['002',45],['003',56]]
avg = sum([e[1] for e in grade_list])/len(grade_list)
print(avg)
40.333333333333336
or you can use for loop
grade_list=[['001',20],['002',45],['003',56]]
sumV = 0
for grade, value in grade_list:
sumV += value
print(sumV / len(grade_list))
40.333333333333336
Or use map and itemgetter
from operator import itemgetter
grade_list=[['001',20],['002',45],['003',56]]
avg = sum(map(itemgetter(1),grade_list))/len(grade_list)
print(avg)
40.333333333333336
Or use mean if is python >= 3.4
from statistics import mean
from operator import itemgetter
grade_list=[['001',20],['002',45],['003',56]]
print(mean(map(itemgetter(1),grade_list)))
40.333333333333336
Or, you can use reduce
from functools import reduce
from operator import itemgetter
grade_list=[['001',20],['002',45],['003',56]]
print(reduce(lambda x, y: x + y/len(grade_list), map(itemgetter(1),grade_list), 0))
40.333333333333336
Or using pandas
import pandas as pd
grade_list=[['001',20],['002',45],['003',56]]
df = pd.DataFrame(grade_list)
print(df.mean(axis=0)[1])
40.3333333333
Here is one way:
grade_list = [['001', 20], ['002', 45], ['003', 56]]
total = 0
for i in grade_list:
total += i[1]
average = total / len(grade_list)
print(average)
Use list indices. For example, replace the variable i in your code with i[1](not the for loop, just whatever you call inside of it). This will have your loop look at the SECOND element in your list, the grade. Right now it just looks at the whole list.
Also, your code is off. You want to go through all the second elements in the list as then divide by the total number of elements, so
average=0
for l in grade_list:
average += l[1]
average/=len(grade_list)
print average
Remember, list indices start at 0.
>>> grade_list=[['001',20],['002',45],['003',56]]
>>> print(round(sum([sublist[1] for sublist in grade_list ]) / len(grade_list),2))
40.33
