Text File Quiz Class 12

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📖 Text File Quiz — Class 12 Computer Science (Code 083)

Practice 20 CBSE Class 12 Computer Science (Code 083) MCQs on text file handling — opening a file in different modes (r, r+, w, w+, a), closing files, the with statement, write()/writelines(), read()/readline()/readlines(), iterating a file with a for loop, and the seek()/tell() methods.

This set includes 4 board-style predict-the-output questions with full working code — including the classic r+ vs w+ truncation trap and a vowel-counting program. Every result below has been verified by actually running the code in Python. Tap any question to reveal the answer with a clear explanation.

📂 Opening Files🔧 File Modes✍️ Writing Files📖 Reading Files🎯 seek() and tell()✅ Best Practices⭐ Board-Style Programs
Q1
📂 Opening Files

How do you open a text file in read mode in Python?

  1. file = open(“example.txt”, “r”)
  2. file = open(“example.txt”, “w”)
  3. file = open(“example.txt”, “a”)
  4. file = open(“example.txt”, “rb”)
Show Answer & Explanation

✅ Answer: (a) file = open(“example.txt”, “r”)

“r” is the mode for reading a text file — it’s also the default mode if you don’t specify one at all.

Q2
🔧 File Modes

Which open mode allows both reading and writing in a text file WITHOUT truncating (emptying) the file?

  1. r
  2. r+
  3. w
  4. w+
Show Answer & Explanation

✅ Answer: (b) r+

r+ opens an existing file for both reading and writing, but keeps its existing content intact. (w+ also allows both, but it truncates the file to empty first — a key difference tested below.)

Q3
🔧 File Modes

What is the purpose of the “a” mode when opening a text file?

  1. Read mode
  2. Write mode
  3. Append mode
  4. Read and Write mode
Show Answer & Explanation

✅ Answer: (c) Append mode

“a” (append mode) opens the file for writing but adds new content to the end, preserving everything already there.

Q4
🔒 Closing Files

How can you close an open text file in Python?

  1. file.close()
  2. close(file)
  3. file.close(file)
  4. close(“file.txt”)
Show Answer & Explanation

✅ Answer: (a) file.close()

file.close() — close() is a method called on the file object itself, not a standalone function.

Q5
✅ Best Practices

What is the benefit of using the ‘with’ statement when opening a file?

  1. It automatically creates a new file
  2. It ensures that the file is closed properly after use
  3. It speeds up file operations
  4. It allows direct manipulation of file data
Show Answer & Explanation

✅ Answer: (b) It ensures that the file is closed properly after use

The with statement is a context manager that guarantees the file gets closed once the block finishes — even if an error occurs partway through — so you never have to remember to call close() yourself.

Q6
✍️ Writing Files

Which method is used to write a single string to a text file in Python?

  1. file.write()
  2. file.writeline()
  3. file.append()
  4. file.add()
Show Answer & Explanation

✅ Answer: (a) file.write()

file.write() writes exactly the string you give it. (writeline(), append(), and add() aren’t real file methods in Python.)

Q7
🎯 seek() and tell()

How can you move the cursor position in a text file to a specific byte using Python?

  1. file.jump(offset)
  2. file.seek(offset)
  3. file.move(offset)
  4. file.position(offset)
Show Answer & Explanation

✅ Answer: (b) file.seek(offset)

file.seek(offset) moves the file’s internal read/write cursor to the given byte position, letting you jump around the file instead of always reading sequentially.

Q8
🎯 seek() and tell()

What does the tell() method return for a text file?

  1. The file’s size
  2. The current line number
  3. The cursor’s current position
  4. The file’s creation time
Show Answer & Explanation

✅ Answer: (c) The cursor’s current position

file.tell() returns the current position of the cursor (as a byte offset from the start), telling you exactly where the next read or write will happen.

Q9
📖 Reading Files

In the context of text files, what does the readline() method do?

  1. Reads a specific line by line number
  2. Reads the entire file at once
  3. Reads a single character
  4. Reads one line, up to and including the next newline character
Show Answer & Explanation

✅ Answer: (d) Reads one line, up to and including the next newline character

readline() reads and returns just one line — from the current cursor position up through the next newline character — each time it’s called.

Q10
✍️ Writing Files

How can you write (append) multiple lines to a text file at once in Python?

  1. file.writelines(“line1”, “line2”)
  2. file.write(“line1\nline2”)
  3. file.append(“line1”, “line2”)
  4. file.writelines([“line1”, “line2”])
Show Answer & Explanation

✅ Answer: (d) file.writelines([“line1”, “line2”])

writelines() takes a single iterable (like a list of strings) as its argument: file.writelines(["line1", "line2"]). It does NOT accept multiple separate string arguments the way the other options suggest.

Q11
📖 Reading Files

Which method is used to read the ENTIRE content of a text file into a single string?

  1. file.read()
  2. file.readline()
  3. file.readlines()
  4. file.readall()
Show Answer & Explanation

✅ Answer: (a) file.read()

file.read() reads everything from the current cursor position to the end of the file, returning it all as one string. (readall() isn’t a real Python file method.)

Q12
🔧 File Modes

What is the purpose of the “w+” mode when opening a text file?

  1. Write mode only
  2. Read mode only
  3. Append mode
  4. Read and Write mode (but the file is truncated to empty first)
Show Answer & Explanation

✅ Answer: (d) Read and Write mode (but the file is truncated to empty first)

“w+” allows both reading and writing, but — unlike "r+" — it immediately truncates the file to empty the moment it’s opened, discarding any existing content.

Q13
🖥️ os Module

How can you check if a file exists before attempting to open it in Python?

  1. file.exists(“example.txt”)
  2. file.open(“example.txt”)
  3. os.path.exists(“example.txt”)
  4. open.file(“example.txt”)
Show Answer & Explanation

✅ Answer: (c) os.path.exists(“example.txt”)

os.path.exists(“example.txt”) returns True or False depending on whether the file is actually present — a safe check before trying to open it.

Q14
🎯 seek() and tell()

What is the purpose of the seek(0) method call on a text file?

  1. Move the cursor to the end of the file
  2. Move the cursor to the very beginning of the file
  3. Move the cursor to a random position
  4. Move the cursor to the start of the next line
Show Answer & Explanation

✅ Answer: (b) Move the cursor to the very beginning of the file

seek(0) resets the cursor to byte position 0 — the very start of the file — commonly used to re-read a file from the beginning after already reading through it once.

Q15
📖 Reading Files

How can you read all lines from a text file into a list in Python?

  1. file.read()
  2. file.readlist()
  3. file.readlines()
  4. file.readall()
Show Answer & Explanation

✅ Answer: (c) file.readlines()

file.readlines() reads every line and returns them as a list of strings, e.g. ['Hello World\n', 'This is Python\n'].

Q16
📖 Reading Files

What is the most Pythonic (idiomatic) way to read a text file line by line, one at a time?

  1. Calling file.readline() manually in an infinite while loop
  2. Using a for loop directly on the file object: for line in file:
  3. Calling file.read() and then splitting on ‘\n’
  4. There is no way to do this in Python
Show Answer & Explanation

✅ Answer: (b) Using a for loop directly on the file object: for line in file:

for line in file: iterates the file object directly, giving you one line per loop iteration — it’s memory-efficient (doesn’t load the whole file at once, unlike readlines()) and is the standard, idiomatic approach.

Q17
⭐ Board-Style Programs

What does the following program print?

with open("t.txt", "w") as f:
    f.write("Hello World\n")
with open("t.txt", "r") as f:
    data = f.read(5)
    pos = f.tell()
print(data, pos)
  1. Hello 5
  2. Hello World 11
  3. World 5
  4. Hello 0
Show Answer & Explanation

✅ Answer: (a) Hello 5

f.read(5) reads only the first 5 characters: “Hello”. After reading those 5 characters, the cursor sits at position 5, which is what tell() reports.

Q18
⭐ Board-Style Programs

What does the following program print? (The file already contains “Hello World\n” before this code runs.)

with open("t.txt", "r+") as f:
    f.write("XXXXX")
with open("t.txt", "r") as f:
    print(f.read())
  1. XXXXX (the entire file is replaced)
  2. XXXXX World (only the first 5 characters are overwritten)
  3. Hello WorldXXXXX (XXXXX is appended)
  4. Error, ‘r+’ cannot be used to write
Show Answer & Explanation

✅ Answer: (b) XXXXX World (only the first 5 characters are overwritten)

r+ mode does not erase the file — it just positions the cursor at the start and lets you write, which overwrites only as many characters as you write. Since “XXXXX” is 5 characters, it replaces “Hello”, leaving the rest untouched: “XXXXX World”.

Q19
⭐ Board-Style Programs

What does the following program print? (The file already contains 3 lines of text before this code runs.)

with open("t.txt", "w+") as f:
    print(repr(f.read()))
  1. The full original 3 lines of text
  2. An empty string: ”
  3. Only the first line
  4. Error, since w+ can’t be used with read()
Show Answer & Explanation

✅ Answer: (b) An empty string: ”

Opening in “w+” mode immediately truncates the file to empty the moment it’s opened — so even though w+ technically supports reading, there’s nothing left to read. This is the classic difference from "r+", which preserves content.

Q20
⭐ Board-Style Programs

What does the following program print? (Counting vowels in a text file that contains: “Hello World\nThis is Python\nCBSE Class 12\n”)

with open("t.txt", "r") as f:
    content = f.read()
vowels = "aeiouAEIOU"
count = sum(1 for ch in content if ch in vowels)
print(count)
  1. 6
  2. 8
  3. 10
  4. 5
Show Answer & Explanation

✅ Answer: (b) 8

Counting every vowel (upper or lower case) across all three lines of the file gives a total of 8 — a classic “read a file and count vowels/characters” suggested program from the CBSE syllabus.

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