返回该部分中所有学生的平均分数

Question

I know it was asked already but the answers the super unclear

The first requirement is to open a file (sadly I have no idea how to do that)
The second requirement is a section of code that does the following:

Each line represents a single student and consists of a student number, a name, a section code and a midterm grade, all separated by whitespace

So I don't think i can target that element due to it being separate by whitespace?

Here is an excerpt of the file, showing line structure

987654322  Xu  Carolyn  L0101   19.5
233432555    Jones  Billy Andrew      L5101   16.0
555432345    Patel  Amrit                 L0101   13.5
888332441    Fletcher Bobby L0201   18
777998713   Van Ryan  Sarah Jane         L5101   20 
877633234    Zhang  Peter             L0102   9.5
543444555    Martin  Joseph           L0101   15    
876543222    Abdolhosseini  Mohammad Mazen  L0102 18.5

I was provided the following hints:

• Notice that the number of names per student varies.
• Use rstrip() to get rid of extraneous whitespace at the end of the lines.

I don't understand the second hint.

This is what I have so far:

counter = 0  
elements = -1  

for sets in the_file  
    elements = elements + 1  
    if elements = 3  

I know it has something to do with readlines() and the targeting the section code.

Answer 1

marks = [float(line.strip().split()[-1]) for line in open('path/to/input/file')]
average = sum(marks)/len(marks)

Hope this helps

Answer 2

Open and writing to files strip method

Something like this?

data = {}
with open(filename) as f:#open a file

    for line in f.readlines():#proceed through file lines

        #next row is to split data using spaces and them skip empty using strip
        stData = [x.strip() for x in line.split() if x.strip()]

        #assign to variables
        studentN, studentName, sectionCode, midtermGrade = stData
        if sectionCode not in data:
            data[sectionCode] = []

        #building dict, key is a section code, value is a tuple with student info
        data[sectionCode].append([studentN, studentName, float(midtermGrade)]

#make calculations
for k,v in data.iteritems():#iteritems returns you (key, value) pair on each iteration
    print 'Section:' + k + ' Grade:' + str(sum(x[2] for x in v['grade']))

Answer 3

more or less:

infile = open('grade_file.txt', 'r')
score = 0
n = 0
for line in infile.readlines():
    score += float(line.rstrip().split()[-1])
    n += 1

avg = score / n