Answer the questions based on the code below with proper justifications.…

(i) Difference Between Text File and Binary File

Byte-Level Difference

• Text files store data as readable characters.
  Each byte (or group of bytes) represents a character using encoding schemes such as ASCII or UTF-8.

• Binary files store data as raw bytes exactly as they are stored in computer memory, without any character encoding.

Why data.pkl Cannot Be Read Properly in a Text Editor

data.pkl is a binary file created using the pickle module.
It contains serialized Python objects in binary form.

When a text editor opens this file, it tries to interpret raw binary bytes as text characters, which results in unreadable or garbled symbols.

(ii) Pickling and Security Risks

Pickling

Pickling is the process of converting Python objects into a byte stream (serialization) so they can be stored in files or transmitted over a network.

Example:

pickle.dump(records, f)

The reverse process is called unpickling.

pickle.load(f)

Security Risk of Unpickling

The pickle module is not secure for untrusted data.

A malicious pickle file may contain harmful instructions that can execute arbitrary code during unpickling.

Condition for Arbitrary Code Execution

During unpickling, Python may automatically execute functions returned by the __reduce__() method of an object.

An attacker can craft a malicious pickle file that calls dangerous functions such as:

os.system()

Thus, if pickle.load() is used on data from an unknown or untrusted source, arbitrary system commands may execute.

(iii) Purpose of newline='' in CSV on Windows

newline='' prevents extra blank lines while writing CSV files on Windows.

The CSV module already handles newline characters internally.

If newline='' is omitted:

• Windows automatically converts \n into \r\n

• The CSV module also writes \r\n

• This causes double newline translation

As a result, extra empty rows appear between records in the CSV file.

Therefore, using:

open('data.csv', 'w', newline='')

ensures correct CSV formatting.

(iv) Program to Read, Merge, Add Grade, and Write results.csv

import pickle
import csv

try:

    # Read data from pickle file
    with open('data.pkl', 'rb') as pf:
        pkl_data = pickle.load(pf)

    # Read data from CSV file
    with open('data.csv', 'r', newline='') as cf:
        reader = csv.DictReader(cf)
        csv_data = list(reader)

    merged_records = []

    # Merge records and assign grades
    for rec in pkl_data:

        score = float(rec['score'])

        grade = 'A' if score >= 90 else 'B'

        merged_records.append({
            'id': int(rec['id']),
            'name': rec['name'],
            'score': score,
            'grade': grade
        })

    # Write output to results.csv
    with open('results.csv', 'w', newline='') as rf:

        fields = ['id', 'name', 'score', 'grade']

        writer = csv.DictWriter(rf, fieldnames=fields)

        writer.writeheader()

        writer.writerows(merged_records)

    print("results.csv created successfully")

except FileNotFoundError:
    print("Error: File not found")

except pickle.UnpicklingError:
    print("Error: Invalid pickle file")

except ValueError as e:
    print("Value Error:", e)

except Exception as e:
    print("Unexpected Error:", e)

Output of results.csv

id,name,score,grade
1,Alice,95.5,A
2,Bob,87.0,B
3,Charlie,91.3,A