无法将数据写入 csv 文件

Question

I am not able to write data into csv file. I was able to separate the header and add new column and also was able to add the total scores, but seems like it is not working

Source File

name,Homework_1,Homework_2
Naveed,20,19
Mahvish,10,18

Target File

name,Homework_1,Homework_2,total
Mahvish,10,18,28.0
Naveed,20,19,39

import csv


def letterGrade(score):
    if score >= 90:
        letter = 'A'
    elif score >= 80:
        letter = 'B'
    elif score >= 70:
       letter = 'C'
    elif score >= 60:
        letter = 'D'
    else:
        letter = 'F'  #fall through or default case
    return letter

with open('marks.csv','r') as r:
    csvReader=csv.reader(r)
 
    header=next(csvReader)
    header.append("total")
    
   
    total=0
    if header!=None:
        for row in csvReader:
            total=0
            for index in range(1,3):
                thisGrade = row[index]
                if thisGrade == '':
                    thisGrade = 0.0  # change a nothing to a zero
                else:
                    thisGrade = float(thisGrade) 
                total = total + thisGrade
            percent = (total  * 100.)/ 200.  # out of a possible 200 points

            gradeToReport = letterGrade(percent)
        
            row.append(total)
            print(row)
            
            
            with open('marks_op.csv','w',newline='') as w:
                
                csvWriter=csv.writer(w,delimiter=',')
                
                csvWriter.writerow(i for i in header)
                #csvWriter.writerows(row)
                csvWriter.writerow(row)
            

Answer 1

You're overwriting the output file in each loop iteration

with open('marks_op.csv','w',newline='') as w:

should be

with open('marks_op.csv','a',newline='') as w:

Answer 2

I have corrected the code. Thanks for solution Mike 67.

import csv


def letterGrade(score):
    if score >= 90:
        letter = 'A'
    elif score >= 80:
        letter = 'B'
    elif score >= 70:
       letter = 'C'
    elif score >= 60:
        letter = 'D'
    else:
        letter = 'F'  #fall through or default case
    return letter


    
with open('marks.csv','r') as r:
    csvReader=csv.reader(r)
 
    header=next(csvReader)
    header.append("total")
    
    with open('marks_op.csv','w',newline='') as w:
        csvWriter=csv.writer(w,delimiter=',')
        csvWriter.writerow(header)
   
    total=0
    if header!=None:
        for row in csvReader:
            total=0
            for index in range(1,3):
                thisGrade = row[index]
                if thisGrade == '':
                    thisGrade = 0.0  # change a nothing to a zero
                else:
                    thisGrade = float(thisGrade) 
                total = total + thisGrade
                
            percent = (total  * 100.)/ 200.  # out of a possible 200 points

            gradeToReport = letterGrade(percent)
            
        
            row.append(total)
            
            with open('marks_op.csv','a',newline='') as x:
                csvWriter=csv.writer(x,delimiter=',')
                csvWriter.writerow(row)