Python file processing?

Question

My assignment was to write a program which extracts the first/last names, birth year, and ID from a file, manipulate that information to create a username and formatted ID, prompt the user for 3 test grades, calculate the average, and finally write all the information to a new file. This is the program I wrote, and the error I got is listed below the program. Define main function

def main():
infile = open("studentinfo.txt", "r")
data = infile.read()
fName, lName, ID, year = data.split(",")
year = int(year)

Prompt the user for three test scores

grades = eval(input("Enter the three test scores separated by a comma: "))

Create a username

uName = (lName[:4] + fName[:2] + str(year)).lower()
converted_id = ID[:3] + "-" + ID[3:5] + "-" + ID[5:]
grade_1, grade_2, grade_3 = grades

Convert the grades to strings so they can be written to a new file

[grade_1, grade_2, grade_3] = [str(grade_1), str(grade_2), str(grade_3)]

Calculate the average

average =(grade_1 + grade_2+ grade_3)/3

Convert the average to a string

average = str(average)

Write the information the file

outfile = open("studentreport.txt", "w")
outfile.write("*******Student Report*******\nStudent Name:" + fName + " " + lName)
outfile.write("\nStudent ID:  " + converted_id + "\n" + "Username:    " + uName + "\n\n")
outfile.write("Grade 1:    " + grade_1 + "\n" "Grade 2:    " + grade_2 + "\n" + "Grade 3:    " + grade_3 + "\n" + "Average:    " + average)   

infile.close()
outfile.close()

main()

Traceback (most recent call last):

File "C:/Users/ovi/Desktop/Python Project 1.py", line 34, in

main()

File "C:/Users/ovi/Desktop/Python Project 1.py", line 22, in main

average =(grade_1 + grade_2+ grade_3)/3

TypeError: unsupported operand type(s) for /: 'str' and 'int'

So, you convert your grades_x to strings, and then try to add them together and divide by 3? Maybe store the string-converted grades in different named variables. Using + with strings concatenates them together, instead of adding. — Greg Hewgill
– Greg Hewgill, Commented Jun 16, 2015 at 3:02

Lazik · Accepted Answer · 2015-06-16 03:05:31Z

1

You need to convert your converted string grades to floats (or int)

average =(float(grade_1) + float(grade_2)+ float(grade_3))/3.0
average = str(average)

answered Jun 16, 2015 at 3:05

Lazik

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1 Comment

Ovi Over a year ago

Oh okay thanks! I think I can also just move the lines around and make the grades as strings AFTER I calculated the average

Avinash Raj · Accepted Answer · 2015-06-16 03:21:04Z

1

You need to convert the variables of type int to strings.

outfile.write("Grade 1:    " + str(grade_1) + "\n" "Grade 2:    " + str(grade_2) + "\n" + "Grade 3:    " + str(grade_3) + "\n" + "Average:    " + str(average))

OR

You could simply do like this..

>>> gr1 = 23
>>> gr2 = 45
>>> gr3 = 56
>>> total = gr1+gr2+gr3
>>> avg = total/3
>>> l = [gr1, gr2, gr3, total, avg]
>>> print("GRade 1: {} grade 2: {} grade 3: {} total: {} average : {}".format(*l))
GRade 1: 23 grade 2: 45 grade 3: 56

edited Jun 16, 2015 at 3:21

answered Jun 16, 2015 at 3:01

Avinash Raj

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5 Comments

Ovi Over a year ago

I tought I did that here though: [grade_1, grade_2, grade_3] = [str(grade_1), str(grade_2), str(grade_3)]

Ovi Over a year ago

And I did a similar thing for the average. Is this wrong?

Avinash Raj Over a year ago

just convert the grades to strings while printing only. Your method of conversion is wrong. It would be, l = [str(grade_1), str(grade_2), str(grade_3)] ; outfile.write("Grade 1: {} .....".format(*l))

Ovi Over a year ago

Thanks for the help! Do you think you could elaborate why my method of conversion is wrong though? I am trying to understand this better, not just memorize it

Avinash Raj Over a year ago

you cant able to find the average for strings.. Do all the calculations with the data type as int.

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