Walkthrough: Putting It Together¶

This guide walks through the thinking process for this exercise. It does NOT give you the complete solution. For that, see SOLUTION.md.

Before reading this¶

Try the exercise yourself first. Spend at least 20 minutes. If you have not tried yet, close this file and open the exercise file.

Understanding the problem¶

This exercise combines everything from Exercises 01-14 into one program: a student grade reporter. It reads student names and scores from a file, calculates grades, computes an average, and lets the user look up a student by name.

The program uses: variables, strings, user input, conditions, lists, dictionaries, loops, functions, and file reading. If you can understand this, you are ready for Level 0.

Planning before code¶

Break the program into four jobs:

Load data -- read student names and scores from a file
Convert scores to grades -- turn numbers into letter grades (A, B, C, D, F)
Calculate stats -- find the average, highest, and lowest scores
Display results -- print a formatted report and handle a student lookup

Step 1: Loading data from a file¶

The data file (../14-reading-files/data/sample.txt) looks like this:

Alice,92
Bob,87
Charlie,95

Each line has a name and a score separated by a comma. You need to read each line, split it on the comma, and store the result.

line = "Alice,92"
parts = line.split(",")
name = parts[0]          # "Alice"
score = int(parts[1])    # 92

Predict before you scroll¶

Why do we need int() around parts[1]? What would happen if we skipped it and tried to compare the score to 90?

Step 2: Converting scores to letter grades¶

This is a classic if/elif/else chain. Think about the order:

def get_letter_grade(score):
    if score >= 90:
        return "A"
    elif score >= 80:
        return "B"
    # ... continue for C, D, F

Why check >= 90 first? Because if you checked >= 60 first, a score of 95 would match that condition and get a "D".

Step 3: Calculating the class average¶

To get an average, you need two things: the total of all scores and the count of students.

total = 0
for student in students:
    total = total + student["score"]
average = total / len(students)

Predict before you scroll¶

If there are 5 students with scores [92, 87, 95, 78, 91], what would the average be?

Step 4: The student lookup¶

The program asks the user to type a student name. You loop through the list and compare names. Using .lower() on both sides makes the search case-insensitive (typing "alice" finds "Alice").

if student["name"].lower() == lookup.lower():
    # found them

Common mistakes¶

Mistake	Why it happens	How to fix
`int("92\n")` crashes	File lines can have newline characters	Use `.strip()` before splitting
Grade logic gives wrong letter	Conditions checked in wrong order	Check highest threshold first (>= 90 before >= 80)
Student lookup is case-sensitive	"alice" does not match "Alice"	Use `.lower()` on both strings before comparing
Division error with empty list	`len(students)` is 0	Check if the list is empty before dividing

What to explore next¶

Add a feature that prints only students who scored below 80
Save the report to a new file using open("report.txt", "w") instead of just printing it