You are an expert CBSE XII CS Computer Science teacher, examiner, and study material creator.

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SCOPE — READ BEFORE GENERATING ANYTHING
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Today's lecture covers ONE topic only: "List and tuple operations"
Lecture number 10 of 91 | Duration: 35 minutes | Board: CBSE
Chapter: Computational Thinking and Programming – 2

HARD RULE: Every piece of content you generate — notes, examples, questions, tips —
must be directly relevant to "List and tuple operations" only.
DO NOT pull content, examples, or questions from any other topic or chapter.

LECTURE MODE: THEORY / CONCEPT TEACHING
- Teach the concept first: definitions, intuition, examples, syntax/steps, and misconceptions.
- Use the given exam-frequency analysis internally to decide emphasis and short concept checks; keep the lecture concept-teaching focused.
- Keep content tightly scoped to today's concept list.

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SECTION 1: LECTURE INFORMATION
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Class: XII CS | Subject: Computer Science | Board: CBSE
Topic: List and tuple operations Theory
Subtopics to cover today:
- List and tuple operations

Student level: Class XII, CBSE Board, average to above-average students preparing for board exams

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SECTION 2: TEACHER'S REFERENCE NOTES
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List and tuple operations Theory

Concept ID: U1_LIST_TUPLE_OPS.
Primary Sub-subtopic: List and tuple operations.
Question-bank grouping: Revision of Python & Core Concepts.

Use this lecture for theory, examples, misconceptions, and short concept checks mapped to this concept ID.

Teaching ideas: Teach the concept first, then use a small number of concept-ID matched concept checks.

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SECTION 3: EXAM FREQUENCY DATA (Year-wise)
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Teaching priority: HIGH
High-yield concepts: List and tuple operations

| Year | Questions | Marks |
|------|-----------|-------|
| 2021 | 7 | 7 |
| 2023 | 8 | 10 |
| 2024 | 12 | 14 |
| 2025 | 9 | 12 |
| 2026 | 4 | 5 |
| **Total** | **40** | **48** |

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SECTION 4: EXAM ANALYSIS INPUT — DO NOT PRINT THESE IN THEORY NOTES
(Scope: "List and tuple operations" only — 40 questions from board papers)
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THEORY LECTURE RULE: use these PYQs only as private analysis data — this lecture is PURELY THEORY.
- Cover every concept and trap revealed by these PYQs in the study notes
- Do NOT print, quote, reproduce, paraphrase, or label any actual PYQ in the final HTML
- Self-generate your own tricky/important questions and examples about the concept itself only —
  do not call them "PYQ-pattern", "PYQ-style", "board-style", or reference PYQs/previous years at all
- In theory lectures, generated questions must be MCQ or Short Answer only
- Never use the word "PYQ" or phrases like "previous year question" anywhere in the visible HTML


--- 2021 Board Exam (7 questions | 7 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
Consider a declaration L = (1, 'Python', '3.14').
Which of the following represents the data type of L?
a) list
b) tuple
c) dictionary
d) string

Q2. [MCQ] [1M] [Easy] Section-A
Given a Tuple tup1= (10, 20, 30, 40, 50, 60, 70, 80, 90).
What will be the output of print(tup1[3:7:2])?
a) (40,50,60,70,80)
b) (40,50,60,70)
c) [40,60]
d) (40,60)

Q3. [MCQ] [1M] [Easy] Section-A
The return type of the input() function is:
a) string
b) integer
c) list
d) tuple

Q4. [MCQ] [1M] [Easy] Section-A
Consider a tuple tup1 = (10, 15, 25, 30). Identify the statement that will result in an error.
a) print(tup1[2])
b) tup1[2] = 20
c) print(min(tup1))
d) print(len(tup1))

Q5. [MCQ] [1M] [Easy] Section-B
Identify the output of the following Python statements.
x = [[10.0, 11.0, 12.0],[13.0, 14.0, 15.0]]
y = x[1][2]
print(y)
a) 12.0
b) 13.0
c) 14.0
d) 15.0

Q6. [MCQ] [1M] [Easy] Section-B
Identify the output of the following Python statements.
lst1 = [10, 15, 20, 25, 30]
lst1.insert(3, 4)
lst1.insert(2, 3)
print(lst1[-5])
a) 2
b) 3
c) 4
d) 20

Q7. [MCQ] [1M] [Easy] Section-B
What will be the output of the following code?
tup1 = (1,2,[1,2],3)
tup1[2][1]=3.14
print(tup1)
a) (1,2,[3.14,2],3)
b) (1,2,[1,3.14],3)
c) (1,2,[1,2],3.14)
d) Error Message

--- 2023 Board Exam (8 questions | 10 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
Given the following Tuple
Tup= (10, 20, 30, 50)
Which of the following statements will result in an error ?
(a) print (Tup[0])
(b) Tup.insert (2,3)
(c) print (Tup[1:2])
(d) print(len(Tup) )

Q2. [MCQ] [1M] [Easy] Section-A
Fill in the blank.
________ function is used to arrange the elements of a list in ascending order.
(a) sort()
(b) arrange ()
(c) ascending()
(d) asort()

Q3. [MCQ] [1M] [Easy] Section-A
Which function returns the sum of all elements of a list ?
(a) count ()
(b) sum()
(c) total()
(d) add()

Q4. [MCQ] [1M] [Easy] Section-A
Fill in the blank :
________ is not a valid built-in function for list manipulations.
(a) count()
(b) length()
(c) append()
(d) extend()

Q5. [MCQ] [1M] [Easy] Section-A
Which of the following statement(s) would give an error during execution of the following code?
tup = (20,30,40,50,80,79)
print(tup)        #Statement 1
print(tup[3]+50)  #Statement 2
print(max(tup))   #Statement 3
tup[4]=80         #Statement 4
a) Statement 1
b) Statement 2
c) Statement 3
d) Statement 4

Q6. [Assertion-Reason] [1M] [Easy] Section-A
Assertion(A): List is an immutable data type.
Reasoning(R): When an attempt is made to update the value of an immutable variable, the old variable is destroyed and a new variable is created by the same name in memory.
a) Both A and R are true and R is the correct explanation for A
b) Both A and R are true and R is not the correct explanation for A
c) A is True but R is False
d) A is false but R is True

Q7. [Output Prediction] [2M] [Easy] Section-B
(a) Given is a Python list declaration :
Listofnames=["Ankit", "Ashish", "Rajan", "Rajat"]
Write the output of :
print (Listofnames [-1:-4:-1])

(b) Consider the following tuple declaration :
tupl=(10,20,30,40)
Write the output of :
print (tupl.index(20))

Q8. [Short Answer] [2M] [Easy] Section-B
Write the Python statement for each of the following tasks using BUILT-IN functions/methods only:
(i) To insert an element 200 at the third position, in the list L1.
(ii) To check whether a string named message ends with a full stop / period or not.

--- 2024 Board Exam (12 questions | 14 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
What will be the output of the following code ?
L=[10,20,30,40,50]
print(L[2:4])
(A) [20,30]
(B) [10,20,30,40]
(C) [30,40]
(D) [30,40,50]

Q2. [MCQ] [1M] [Easy] Section-A
Fill in the blank:
________ is the method of a list which is used to add an element in the end of the existing list.
(A) append()
(B) add()
(C) insert()
(D) extend()

Q3. [Short Answer] [1M] [Easy] Section-A
State True or False :
"In Python, tuple is a mutable data type".

Q4. [MCQ] [1M] [Easy] Section-A
For the following Python statement :
N = (25)
What shall be the type of N ?
(A) Integer
(B) String
(C) Tuple
(D) List

Q5. [MCQ] [1M] [Easy] Section-A
What will be the output of the following code?
tuple1 = (1, 2, 3)
tuple2 = tuple1
tuple1 += (4,)
print(tuple1 == tuple2)
a) True
b) False
c) tuple1
d) Error

Q6. [MCQ] [1M] [Easy] Section-A
What does the list.remove(x) method do in Python?
a) Removes the element at index x from the list
b) Removes the first occurrence of value x from the list
c) Removes all occurrences of value x from the list
d) Removes the last occurrence of value x from the list

Q7. [Short Answer] [1M] [Easy] Section-B
If L1=[1,2,3,2,1,2,4,2, . . . ], and L2=[10,20,30, . . .], answer using built-in functions only.
Write a statement to count the occurrences of 4 in L1.

Q8. [Short Answer] [1M] [Easy] Section-B
If L1=[1,2,3,2,1,2,4,2, . . . ], and L2=[10,20,30, . . .], answer using built-in functions only.
Write a statement to sort the elements of list L1 in ascending order.

Q9. [Short Answer] [1M] [Easy] Section-B
If L1=[1,2,3,2,1,2,4,2, . . . ], and L2=[10,20,30, . . .], answer using built-in functions only.
Write a statement to insert all the elements of L2 at the end of L1.

Q10. [Short Answer] [1M] [Easy] Section-B
If L1=[1,2,3,2,1,2,4,2, . . . ], and L2=[10,20,30, . . .], answer using built-in functions only.
Write a statement to reverse the elements of list L2.

Q11. [Output Prediction] [2M] [Easy] Section-B
Write the output of the following Python code:
List=[10,20,30]
List.extend([40,50])
print(List)
print(List.index(40))
print(List.count(10))

Q12. [Short Answer] [2M] [Easy] Section-B
(a) Write the Python statement for each of the following tasks using BUILT-IN functions/methods only :
(i) To delete an element 10 from the list lst.
(ii) To replace the string "This" with "That" in the string str1.

--- 2025 Board Exam (9 questions | 12 marks) ---

Q1. [Short Answer] [1M] [Easy] Section-A
State True or False:
"A Python List must always contain all its elements of same data type."

Q2. [MCQ] [1M] [Easy] Section-A
Consider the statements given below and then choose the correct output from the given options:
L=['TIC', 'TAC']
print(L[::-1])
(A) ['crT', 'caT']
(B) ['TIc', 'TAC']
(C) ['car', 'CIT']
(D) ['TAC', 'TIC']

Q3. [Short Answer] [1M] [Easy] Section-A
State if following statement is True or False:
If T is a tuple and L is a list, then T+L is a valid statement in Python.

Q4. [Output Prediction] [1M] [Easy] Section-A
What will be the output of the following code segment ?
p=list("Session 2024–25")
print(p[10:20:])

Q5. [MCQ] [1M] [Easy] Section-A
Which of the following list methods accepts exactly 2 parameters ?
(A) append()
(B) extend()
(C) insert()
(D) pop()

Q6. [MCQ] [1M] [Easy] Section-A
What will be the output of the following code?
L = ["India", "Incredible", "Bharat"]
print(L[1][0] + L[2][-1])
a) IT
b) it
c) It
d) iT

Q7. [Assertion-Reason] [1M] [Easy] Section-A
Assertion (A): The expression (1, 2, 3, 4).append(5) in Python will modify the original sequence datatype.
Reason (R): The append() method adds an element to the end of a list and modifies the list in place.
a) Both A and R are True and R is the correct explanation for A.
b) Both A and R are True and R is not the correct explanation for A.
c) A is True but R is False.
d) A is False but R is True.

Q8. [Programming] [2M] [Easy] Section-B
A. (Answer using Python built-in methods/functions only):
I. Write a statement to find the index of the first occurrence of the substring "good" in a string named review.
II. Write a statement to sort the elements of list L1 in descending order.

Q9. [Output Prediction] [3M] [Medium] Section-C
B. Predict the output of the following Python code:
wildlife_sanctuary = ["Kaziranga", "Ranthambhore", "Jim Corbett", "Sundarbans", "Periyar", "Gir", "Bandipur"]
output = [ ]
for sanctuary in wildlife_sanctuary:
    if sanctuary[-1] in 'aeiou':
        output.append(sanctuary[0].upper())
print(output)

--- 2026 Board Exam (4 questions | 5 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
What is the output of the following code snippet ?
s = 'War and Peace by Leo Tolstoy'
print(s.partition("by"))
(A) ('War and Peace ', 'by', ' Leo Tolstoy')
(B) ['War and Peace ', 'by', ' Leo Tolstoy']
(C) ('War and Peace ', ' Leo Tolstoy')
(D) ['War and Peace ', ' Leo Tolstoy']

Q2. [MCQ] [1M] [Easy] Section-A
What will be the output of the following code snippet ?
t = tuple('tuple')
t2 = t[2],
t += t2
print(t)
(A) ('tuple')
(B) ('tuple','p')
(C) ('t', 'u', 'p', 'l', 'e', 'p')
(D) ('t', 'u', 'p', 'l', 'e')

Q3. [Assertion-Reason] [1M] [Easy] Section-A
Assertion (A) : [1,2,3]+'123' is an invalid expression in Python.
Reason (R) : In Python, a list cannot be concatenated with a string.
(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation for Assertion (A).
(B) Both Assertion (A) and Reason (R) are true and Reason (R) is not the correct explanation for Assertion (A).
(C) Assertion (A) is true, but Reason (R) is false.
(D) Assertion (A) is false, but Reason (R) is true.

Q4. [Short Answer] [2M] [Easy] Section-B
Write a Python statement to perform the following tasks : (USE BUILT_IN FUNCTIONS / METHODS ONLY)
(i) To create a new list L1 containing the elements of list L arranged in ascending order, without modifying list L.
(ii) A statement to check whether the given character, ch is an alphabet or a number.

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QUESTION PATTERN BANK (What the board actually asks for THIS topic)
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Scope: ONLY questions for today's lecture topic are listed below.
DO NOT import questions from other topics or chapters.
These are concept-pattern summaries (what TYPE the board asks), not copies of the
actual questions — never reproduce full question text here.

### Concept: List and tuple operations
  Pattern: Assertion-Reason=3, MCQ=22, Output Prediction=4, Programming=1, Short Answer=10 | Marks: 1M=33, 2M=6, 3M=1 | Total: 40 questions
  [MCQ] [1M] [Easy] × 12
    → Core concept of List and tuple operations
  [MCQ] [1M] [Easy] × 10
    → Output/result interpretation for the current concept
  [Assertion-Reason] [1M] [Easy] × 3
    → Core concept of List and tuple operations
  [Output Prediction] [2M] [Easy] × 2
    → Output/result interpretation for the current concept
  [Short Answer] [2M] [Easy] × 3
    → Core concept of List and tuple operations
  [Short Answer] [1M] [Easy] × 3
    → True/False: core concept of List and tuple operations
  [Short Answer] [1M] [Easy] × 4
    → Core concept of List and tuple operations
  [Output Prediction] [1M] [Easy]
    → Output/result interpretation for the current concept
  [Programming] [2M] [Easy]
    → Core concept of List and tuple operations
  [Output Prediction] [3M] [Medium]
    → Output/result interpretation for the current concept


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IMPORTANCE ANALYSIS (allocate teaching time by this ranking)
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| Rank | Concept | Score | Times Tested | Total Marks | Recent Years | Priority |
|------|---------|-------|-------------|-------------|--------------|----------|
| 1 | List and tuple operations | 150 | 40 | 48M | 2026, 2025, 2024 | CRITICAL |

CRITICAL concepts → full sub-section + comparison table + 2 worked examples
HIGH concepts     → 1 sub-section + 1 worked example
MEDIUM concepts   → definition + 1 quick example only

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EXAMINER FINGERPRINT — TRAPS TO COVER INTERNALLY
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Use the exam-frequency input only for internal analysis. Do not print, quote, reproduce, paraphrase, or label any actual board question in the final HTML.

For this lecture, the generated teaching material must strongly cover these traps:

No static trap list exists yet for "List and tuple operations". Self-generate 4–7 traps from:
- actual question patterns for List and tuple operations
- common wrong assumptions students make about this concept
- output-tracing traps
- syntax-vs-runtime traps
- comparison traps
- order/sequence traps

Important: this list should be treated as dynamic — for lectures with no static trap list, generate traps yourself from the categories above rather than leaving this section thin.
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YOUR TASK — Generate a complete classroom-ready teaching package
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Output format: FULL HTML (print-ready, A4, same format as CBSE study material).
Use the CSS classes below. NO plain Markdown — use HTML elements only.

HTML STRUCTURE TO GENERATE:

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body.bw-mode .def-box, body.bw-mode .key-box, body.bw-mode .example-box,
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body.bw-mode table th { background:#eee !important; color:#000 !important; }
body.bw-mode tr:nth-child(even) { background:#fff !important; }
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</head>
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<button id="btnExitRead" onclick="toggleReadMode()">&#10005; Exit Read Mode</button>

<!-- JS: print modes + collapsible sections + TOC auto-build -->
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<!-- TOC SIDEBAR -->
<nav class="toc-sidebar" aria-label="Table of Contents">
  <h4>&#128214; Contents</h4>
  <!-- TOC links auto-built by JS above -->
</nav>

<!-- MAIN CONTENT -->
<div class="main-content">

Generate these sections in order (all inside the main-content div):

<h1 id="top">List and tuple operations Theory — Lecture 10</h1>
<p style="text-align:center;color:#555;font-size:8.5pt;">CBSE | XII CS | Computational Thinking and Programming – 2 | 35 min</p>

<h2 id="s1">1. Learning Objectives</h2>
[3–5 objectives derived from the exam-importance analysis above (never naming PYQs) — use &lt;ul&gt;&lt;li&gt;]

<h2 id="s2">2. 35-Minute Lecture Flow</h2>
[HTML table: Time | Activity | Teacher Action — include a concept-based recap/check slot — no PYQ discussion, no PYQ wording anywhere]

<h2 id="s3">3. Concept Notes</h2>
[For EVERY sub-concept surfaced by the exam-frequency analysis, never naming or displaying actual board questions:
  - .def-box for definition with "In exam language: ..." line
  - .key-box with syntax/rules as &lt;ul&gt;&lt;li&gt;
  - .example-box for worked examples
  - &lt;pre&gt;&lt;code&gt; for code with .kw/.bi/.st/.cm/.nm token spans
  - .recall-box for output with exact expected output
  - after each important concept, embed 1–2 self-generated MCQ or Short Answer checks about THIS concept only
  - every Section 3 check question must hide its answer inside:
    &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;answer/explanation&lt;/details&gt;
  - do not label any question as PYQ, previous year, board-style, PYQ-pattern, or PYQ-style
  - do not use .pyq-box or .pyq-meta here (in Combined mode .pyq-box is reserved for Section 7)
]

<h2 id="s4">4. Examiner Tricks &amp; Common Mistakes</h2>
[Create one .warn-box for each trap from the EXAMINER FINGERPRINT section.
Each .warn-box must be specific and must include:
  - the mistake students commonly make
  - the correct rule
  - a tiny example or wrong-vs-right explanation
Do not mention actual board questions, years, previous papers, PYQ, or source metadata.]

<h2 id="s5">5. Board Work Plan</h2>
[Numbered list: exactly what to write on the blackboard, in order]

<h2 id="s6">6. Classroom Practice Questions</h2>
[Self-generated from the examiner-trap patterns analysed above — never call these PYQ-pattern/PYQ-style/board-style. CRITICAL: every answer MUST be inside &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;...&lt;/details&gt; — never expose the answer directly.

3×1M MCQ + 5×1-2M Short Answer only.
Theory lecture restriction:
- Do NOT include actual PYQs.
- Do NOT include programming/long-answer/HOTS questions in theory lecture practice.
- Frame original MCQ/Short Answer questions from exam-frequency concepts and examiner traps only.
- Every question must map to one concept/trap discovered in Section 4.

MCQ structure:
&lt;div class="mcq-box"&gt;
  &lt;b&gt;Q1.&lt;/b&gt; Question text?&lt;br&gt;
  &lt;ul class="options"&gt;
    &lt;li&gt;a) ...&lt;/li&gt;
    &lt;li&gt;b) ...&lt;/li&gt;
    &lt;li&gt;c) ...&lt;/li&gt;
    &lt;li&gt;d) ...&lt;/li&gt;
  &lt;/ul&gt;
  &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;
    &lt;ul class="options"&gt;
      &lt;li class="wrong"&gt;a) ... — reason why wrong&lt;/li&gt;
      &lt;li class="correct"&gt;b) ... ✓ — reason why correct&lt;/li&gt;
      ...
    &lt;/ul&gt;
  &lt;/details&gt;
&lt;/div&gt;

Short-answer structure:
&lt;div class="self-test-box"&gt;&lt;b&gt;Q4.&lt;/b&gt; Question&lt;br&gt;&lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;Full answer&lt;/details&gt;&lt;/div&gt;]



<h2 id="s7">7. Student Notes (Copy-ready)</h2>
[Concise notes — every concept highlighted by the exam-frequency analysis, written purely as concept notes (no PYQ wording) — in .key-box and .def-box; self-check questions in .self-test-box with &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;answer&lt;/details&gt;]

<h2 id="s8">8. Homework</h2>
[DYNAMIC HOMEWORK — match this concept and the question types the board actually uses for it
(self-generate the questions; never label them as previous-year or board questions):
- 2×1M (MCQ / very-short answer)
- 2×2M short answer
- 1×3M short answer (or, for a coding topic, a short program / output-prediction question)
- You MAY include one 3–5M long-answer or programming question (this concept supports it)
Dynamic rule: include a 5M long-answer or a programming question ONLY when this concept is genuinely
assessed that way; never force unsupported marks (e.g. a 5M) or question types. same concept — self-generated, never labelled as PYQ-pattern or board-style.
Mark difficulty with .critical/.high/.medium tag.
EVERY answer wrapped in &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;...&lt;/details&gt; inside .self-test-box or .mcq-box]

<h2 id="s9">9. Exam Tips</h2>
[5 specific tips as .tip-box — derived from examiner traps for THIS topic only — written as plain tips, no PYQ wording]

<h2 id="s10">10. Last-Minute Revision Cards</h2>
&lt;div class="card-grid"&gt;
[One .card per concept: &lt;div class="card-title"&gt;[concept]&lt;/div&gt; + 1 rule + 1 example]
&lt;/div&gt;

</div><!-- end .main-content -->
</body>
</html>

HARD OUTPUT RULES:
- Output ONLY the HTML document starting with &lt;!DOCTYPE html&gt;
- Do NOT wrap the output in markdown code fences.
- Do NOT add explanatory text before or after the HTML.
- Use ONLY content from the lecture topic ("List and tuple operations").
- Do NOT include content from other topics.
- The exam-frequency input is private analysis only.
- Final visible HTML must NOT include:
    * actual board question text
    * year labels
    * section labels from papers
    * previous-paper metadata
    * the word "PYQ"
    * phrases like "previous year question", "PYQ-style", "PYQ-pattern", or "board-style"
- Every question, example, and practice item in the final HTML must be self-generated and concept-focused.
- Always finish the document completely through &lt;/html&gt;.
- If the answer becomes long, keep Section 3 complete first, then make Sections 7–10 compact instead of truncating.
- However many concepts the analysis surfaces, self-generate enough Section 3 and Section 6 checks to cover all important traps.
- Never dump real board questions to compensate for a large question pool.

ANSWER HIDING RULES:
- Section 3 concept checks: every answer must be hidden inside &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;...&lt;/details&gt;.
- Section 6 MCQs: options must be listed without .correct or .wrong before details.
- Section 6 MCQ answer analysis must appear only inside &lt;details&gt;.
- Section 6 short-answer questions: every answer must be hidden inside &lt;details&gt;.
- Section 7 self-check questions: every answer must be hidden inside &lt;details&gt;.
- Section 8 homework: every answer must be hidden inside &lt;details&gt;.
- The beforeprint JS already auto-opens all &lt;details&gt; for printing; never remove or skip this feature.

THEORY LECTURE STRUCTURE RULE:
- This theory lecture has no visible board-question discussion section.
- Sections 7–10 are allowed and required:
    Section 7: Student Notes
    Section 8: Homework
    Section 9: Exam Tips
    Section 10: Last-Minute Revision Cards

CODE SIZE RULE:
- Inline code must appear almost the same size as surrounding normal text.
- Do NOT use fixed 8.5pt size for all &lt;code&gt; elements.
- Use code { font-size:0.95em; } for inline code.
- Use pre { font-size:8.5pt; } for block code.
- Use pre code { font-size:inherit; } so code blocks remain compact.
- Inline code inside paragraphs, tables, boxes, tips, questions, and answers must not look smaller than nearby text.

BOX / CLASS USAGE RULES:
- Do NOT use .pyq-box or .pyq-meta in theory lectures.
- Use .mcq-box for MCQs.
- Use .self-test-box for short-answer checks and homework.
- Use .warn-box for examiner traps.
- Use .tip-box for exam tips.
- Use .def-box and .key-box for notes.
- Use .example-box for worked examples.
- Use .recall-box for exact output.

HTML TEMPLATE RULES:
- All generated content must go inside &lt;div class="main-content"&gt;.
- The &lt;nav class="toc-sidebar"&gt; is already present in the template.
- JS auto-builds TOC links from h2/h3 headings.
- Print buttons including Read Mode are already present in the template.
- Do NOT add print buttons again.
- Include the full CSS and JS exactly as given.