Samacheer Kalvi 12th Computer Science Chapter 13 Python & CSV Files Exercise Solutions | KalviGavani

Chapter 13 — Python and CSV Files: Exercise Solutions Guide

How to Use This Page

1. Attempt every exercise in your Samacheer Kalvi textbook on your own first. 2. Compare your answers with the solutions below — focus on the method, not just the final result. 3. Practise the Python programs on a computer; copy-pasting alone will not build exam skills. 4. Review the Common Mistakes and Exam Checklist before your exam.

Key Concepts

File Modes in Python

CSV Module Functions

The with Statement

with open("file.csv", "r") as f:
    # file automatically closes when block ends
    pass

Using with ensures the file is closed even if an exception occurs.

Multiple Choice Questions

Q1. Which module is imported to handle CSV files in Python?

• (a) file   (b) csv   (c) pandas   (d) excel

Q2. What does csv.reader() return?

• (a) A dictionary   (b) A list of strings   (c) An iterator of lists   (d) A tuple

Q3. Which argument prevents extra blank lines when writing CSV on Windows?

• (a) encoding='utf-8'   (b) newline=''   (c) delimiter=','   (d) mode='w'

Q4. csv.DictReader() reads each row as:

• (a) A list   (b) A tuple   (c) A dictionary   (d) A set

Q5. Which file mode opens a file for appending without overwriting?

• (a) 'r'   (b) 'w'   (c) 'a'   (d) 'x'

Q6. What does writerow() do?

• (a) Reads one row   (b) Writes one row to the CSV file   (c) Deletes a row   (d) Sorts rows

Fill in the Blanks

1. The function used to open a file in Python is ______. → open() 2. The with statement ensures the file is ______ automatically after the block ends. → closed 3. csv.writer() returns a writer object that has methods ______() and writerows(). → writerow 4. In DictReader, the keys of each row dictionary come from the ______ row of the file. → header / first 5. The file mode 'w' ______ an existing file before writing. → overwrites / truncates 6. To write multiple rows at once, use the ______ method of a csv writer. → writerows()

True or False

Match the Following

Short Answer Questions

Q1. Explain file opening modes in Python.

Q2. What is the with statement? Why is it preferred for file handling?

The with statement is a context manager that ensures a file is automatically closed after the block, even if an exception occurs.

# Preferred — auto close
with open("data.csv", "r") as f:
    data = f.read()

# Without with — must close manually
f = open("data.csv", "r")
data = f.read()
f.close()  # easy to forget

Q3. Differentiate between csv.reader() and csv.DictReader().

Q4. Write the syntax for csv.writer() and writerow().

import csv

with open("output.csv", "w", newline="") as f:
    w = csv.writer(f)
    w.writerow(["Name", "Age", "City"])
    w.writerow(["Arun", 18, "Chennai"])

Q5. How do you read a CSV file line by line?

import csv

with open("data.csv", "r") as f:
    reader = csv.reader(f)
    for row in reader:
        print(row)  # row is a list like ['Arun', '18', 'Chennai']

Detailed Answer Questions

Q1. Write a Python program to create a CSV file with student details (Roll No, Name, Mark) and write 3 records.

import csv

# Data to write
students = [
    ["Roll No", "Name", "Mark"],
    [1, "Arun", 95],
    [2, "Bala", 88],
    [3, "Chitra", 76]
]

# Write to CSV
with open("student.csv", "w", newline="") as f:
    writer = csv.writer(f)
    writer.writerows(students)

print("student.csv created successfully.")

Output in student.csv:

Q2. Write a Python program to read a CSV file and display all rows using csv.reader().

import csv

with open("student.csv", "r") as f:
    reader = csv.reader(f)
    for row in reader:
        # Each row is a list of strings
        print(row)

Sample output:

Q3. Write a Python program using DictReader to read a CSV file and print each row as a dictionary.

import csv

with open("student.csv", "r") as f:
    reader = csv.DictReader(f)
    for row in reader:
        print(row)  # row is a dict: {'Roll No': '1', 'Name': 'Arun', 'Mark': '95'}
        print(f"Name: {row['Name']}, Mark: {row['Mark']}")

Sample output:

Q4. Write a Python program using DictWriter to write student records to a CSV file.

import csv

fields = ["Roll No", "Name", "Mark"]

rows = [
    {"Roll No": "1", "Name": "Arun", "Mark": "95"},
    {"Roll No": "2", "Name": "Bala", "Mark": "88"},
    {"Roll No": "3", "Name": "Chitra", "Mark": "76"}
]

with open("student_dict.csv", "w", newline="") as f:
    writer = csv.DictWriter(f, fieldnames=fields)
    writer.writeheader()  # Write header row
    writer.writerows(rows)

print("student_dict.csv created successfully.")

Q5. Write a Python program to append a new record to an existing CSV file.

import csv

new_record = [4, "Deepa", 91]

with open("student.csv", "a", newline="") as f:
    writer = csv.writer(f)
    writer.writerow(new_record)

print("Record appended successfully.")

# Verify by reading
with open("student.csv", "r") as f:
    reader = csv.reader(f)
    for row in reader:
        print(row)

Q6. Write a Python program that reads a CSV file containing marks and calculates the average mark.

import csv

total = 0
count = 0

with open("student.csv", "r") as f:
    reader = csv.DictReader(f)  # Skip header automatically
    for row in reader:
        mark = int(row["Mark"])
        total += mark
        count += 1

if count > 0:
    average = total / count
    print(f"Total Marks: {total}")
    print(f"Number of Students: {count}")
    print(f"Average Mark: {average:.2f}")
else:
    print("No student records found.")

Common Mistakes

Exam Checklist

• [ ] Can explain file modes ('r', 'w', 'a', 'r+', 'x')
• [ ] Can write a program to create and write a CSV file using csv.writer()
• [ ] Can read a CSV file using csv.reader() and iterate through rows
• [ ] Can use csv.DictReader() to read rows as dictionaries
• [ ] Can use csv.DictWriter() to write dictionaries to CSV
• [ ] Know the difference between writerow() and writerows()
• [ ] Understand the with statement and why it is preferred
• [ ] Know why newline='' is needed when writing CSV files
• [ ] Can append records to an existing CSV file
• [ ] Can process CSV data (calculate totals, averages, search, filter)