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: "Built-in modules and library functions"
Lecture number 20 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 "Built-in modules and library functions" only.
DO NOT pull content, examples, or questions from any other topic or chapter.

LECTURE MODE: COMBINED THEORY + PYQ (single slot)
- Scope: "Built-in modules and library functions" only.
- First half: teach the core concept (definitions, intuition, key examples, misconceptions) -- keep it tight.
- Second half: switch to previous-year-question practice -- question analysis, marking points, model answers, and common mistakes.
- Use the 11 real PYQ record(s) provided below as the source of truth. Do not fabricate board years, marks, or questions.

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SECTION 1: LECTURE INFORMATION
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Class: XII CS | Subject: Computer Science | Board: CBSE
Topic: Built-in modules and library functions Theory + PYQ
Subtopics to cover today:
- Built-in modules and library functions

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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Built-in modules and library functions Theory + PYQ

COMBINED THEORY + PYQ (single slot).
Concept ID: U1_MODULES_LIBRARY.
Primary Sub-subtopic: Built-in modules and library functions.
Question-bank grouping: Functions and Modules.

Teach the core theory first, then spend the remainder of the lecture on previous-year questions whose concept_ids include U1_MODULES_LIBRARY.

Teaching ideas: Concept first, then a focused PYQ round with board solutions and examiner traps.

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SECTION 3: EXAM FREQUENCY DATA (Year-wise)
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Teaching priority: HIGH
High-yield concepts: Built-in modules and library functions

| Year | Questions | Marks |
|------|-----------|-------|
| 2021 | 1 | 1 |
| 2023 | 3 | 3 |
| 2024 | 3 | 4 |
| 2025 | 3 | 4 |
| 2026 | 1 | 2 |
| **Total** | **11** | **14** |

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SECTION 4: EXAM ANALYSIS INPUT + ACTUAL PYQ SOURCE (printed only in Section 7)
(Scope: "Built-in modules and library functions" only — 11 questions from board papers)
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COMBINED THEORY + PYQ RULE:
Use the provided PYQs in two different ways:
1. Theory sections:
   - Use PYQs only as internal analysis data.
   - Do not print actual PYQ text in concept notes, examples, classroom practice, student notes, homework, or exam tips.
   - Use PYQs to identify concepts, traps, wording patterns, and marking points.
2. PYQ Discussion section (Section 7):
   - Print and discuss actual PYQs.
   - Include year, marks, type, full question text, concept tested, model answer, and common mistake.
   - If the source pool has 15 or fewer PYQs, include ALL actual PYQs.
   - If the source pool has more than 15 PYQs, fully discuss the highest-yield 15 and compactly list the rest with concept tested + exam trap.
For this lecture: source pool has 11 PYQs, so include ALL 11 actual PYQs in the PYQ Discussion section.


--- 2021 Board Exam (1 question | 1 marks) ---

Q1. [MCQ] [1M] [Easy] Section-B
What will be the output of the following code?
import random
List=["Delhi","Mumbai","Chennai","Kolkata"]
for y in range(4):
    x = random.randint(1,3)
    print(List[x],end="#")
a) Delhi#Mumbai#Chennai#Kolkata#
b) Mumbai#Chennai#Kolkata#Mumbai#
c) Mumbai# Mumbai #Mumbai # Delhi#
d) Mumbai# Mumbai #Chennai # Mumbai

--- 2023 Board Exam (3 questions | 3 marks) ---

Q1. [Assertion-Reason] [1M] [Easy] Section-A
Assertion (A) : To use a function from a particular module, we need to import the module.
Reason (R) : import statement can be written anywhere in the program, before using a function from that module.
(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.

Q2. [MCQ] [1M] [Easy] Section-A
What possible output(s) will be obtained when the following code is executed?
import random
myNumber=random.randint(0,3)
COLOR=["YELLOW","WHITE","BLACK","RED"]
for I in range(1,myNumber):
    print(COLOR[I],end="*")
    print()
a) RED*
   WHITE*
   BLACK*
b) WHITE*
   BLACK*
c) WHITE* WHITE*
   BLACK* BLACK*
d) YELLOW*
   WHITE*WHITE*
   BLACK* BLACK* BLACK*

Q3. [Assertion-Reason] [1M] [Easy] Section-A
Assertion(A): Python Standard Library consists of various modules.
Reasoning(R): A function in a module is used to simplify the code and avoids repetition.
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

--- 2024 Board Exam (3 questions | 4 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
Predict the output of the following Python statements :
>>>import statistics as s
>>>s.mode ([10, 20, 10, 30, 10, 20, 30])
(A) 30
(B) 20
(C) 10
(D) 18.57

Q2. [MCQ] [1M] [Easy] Section-A
Which of the following output will never be obtained when the given code is executed ?
import random
Shuffle = random.randrange(10)+1
Draw = 10*random.randrange(5)
print ("Shuffle", Shuffle, end="#")
print ("Draw", Draw)
(A) Shuffle 1 # Draw 0
(B) Shuffle 10 # Draw 10
(C) Shuffle 10 # Draw 0
(D) Shuffle 11 # Draw 50

Q3. [MCQ] [2M] [Easy] Section-B
Identify the correct output(s) of the following code. Also write the minimum and the maximum possible values of the variable b.
import random
a="Wisdom"
b=random.randint(1,6)
for i in range(0,b,2):
    print(a[i],end='#')
a) W#
b) W#i#
c) W#s#
d) W#i#s#

--- 2025 Board Exam (3 questions | 4 marks) ---

Q1. [Short Answer] [1M] [Easy] Section-A
State if the following statement is True or False:
Using the statistics module, the output of the below statements will be 20:
import statistics
statistics.median([10, 20, 10, 30, 10, 20, 30])

Q2. [MCQ] [1M] [Easy] Section-A
What possible output is expected to be displayed on the screen at the time of execution of the Python program from the following code?
import random
L=[10,30,50,70]
Lower=random.randint(2,2)
Upper=random.randint(2,3)
for K in range(Lower, Upper+1):
    print(L[K], end="@")
a) 50@70@
b) 90@
c) 10@30@50@
d) 10@30@50@70@

Q3. [MCQ] [2M] [Easy] Section-B
Identify the correct possible output(s) of the following code segment. Also write the minimum and the maximum possible values of the variable b.
import random
s="War and Peace"
a=len(s)//2
for i in range(4):
    b=random.randrange(i,a)
    print(s[b],end='+')

(A) n+P+d+a+
(B) W+r+n+n+
(C) e+r+W+a+
(D) a+P+e+r+

--- 2026 Board Exam (1 question | 2 marks) ---

Q1. [MCQ] [2M] [Easy] Section-B
What possible output(s) from the given options will NOT be displayed when the following code is executed ? Also, mention, for how many iterations the for loop in the given code will run ?
import random
a = [1,2,3,4,5,6]
for i in range(4):
    j = random.randrange(i,5)
    print(a[j],end='-')
print()

Options :
(A) 3-4-5-4-
(B) 2-2-4-5-
(C) 4-3-3-5-
(D) 5-1-2-4-

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QUESTION PATTERN BANK (What the board actually asks for THIS topic)
===========================================
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: Built-in modules and library functions
  Pattern: Assertion-Reason=2, MCQ=8, Short Answer=1 | Marks: 1M=8, 2M=3 | Total: 11 questions
  [MCQ] [1M] [Easy] × 5
    → Output/result interpretation for the current concept
  [Assertion-Reason] [1M] [Easy] × 2
    → Core concept of Built-in modules and library functions
  [MCQ] [2M] [Easy] × 3
    → Output/result interpretation for the current concept
  [Short Answer] [1M] [Easy]
    → True/False: 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 | Built-in modules and library functions | 53 | 11 | 14M | 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
===========================================

Use the exam-frequency input and actual PYQs to identify traps, marking points, and common mistakes.
For Combined Theory + PYQ mode:
* In theory sections, do not print actual PYQs.
* In Section 7 PYQ Discussion, actual PYQs must be printed and discussed.
* Use these traps to strengthen both concept notes and PYQ explanations.

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

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

If another Combined Theory + PYQ topic has no static trap list, generate topic-specific traps from the actual question pattern bank, not from generic categories like output tracing or order/sequence unless the topic genuinely needs them.
===========================================
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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<!-- 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">Built-in modules and library functions Theory + PYQ — Lecture 20</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 — split the 35-minute lecture into: 15-18 min tight concept teaching; 4-5 min examiner traps and misconception correction; 10-12 min actual PYQ discussion; 2-3 min recap/exit check — use wording such as Theory teaching, concept check, PYQ discussion, model answer, marking point, common mistake; do NOT make the flow pure theory-only]

<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.
Combined mode theory-section 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. PYQ Discussion / Board Questions</h2>
[Since this is Combined Theory + PYQ mode, this section MUST include actual PYQs.

Source pool has 11 PYQs. Because 11 &lt;= 15, include ALL 11 actual PYQs.

For each PYQ, use this structure:
  &lt;div class="pyq-box"&gt;
    &lt;div class="pyq-meta"&gt;[YEAR] · [X] Marks · [TYPE] · Section-[S]&lt;/div&gt;
    &lt;b&gt;Q.&lt;/b&gt; [full actual question text]&lt;br&gt;&lt;br&gt;
    &lt;b&gt;Concept tested:&lt;/b&gt; [concept name]&lt;br&gt;
    &lt;details&gt;&lt;summary&gt;▶ View Model Answer&lt;/summary&gt;
      &lt;b&gt;Model Answer:&lt;/b&gt; [answer]&lt;br&gt;
      &lt;b&gt;Marking point:&lt;/b&gt; [what the examiner expects]&lt;br&gt;
      &lt;b&gt;Common mistake:&lt;/b&gt; [student mistake]
    &lt;/details&gt;
  &lt;/div&gt;

Rules:
* Include all 11 actual PYQs.
* Do not fabricate year, marks, section, or question text.
* Model answer, marking point, and common mistake must be hidden inside &lt;details&gt;.
* Question text and concept tested may remain visible.
* Order Easy to Tough; within difficulty, order 1M → 2M → 3M → 4/5M.
* If all questions are 1M, group them logically by concept pattern (e.g. identifiers, keywords, comments, Python basics).]

<h2 id="s8">8. 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="s9">9. Homework</h2>
[Homework must follow the actual exam pattern for this topic:
- 4×1M MCQ
- 4×1M Short Answer / True-False / one-line answer
- 2×2M Short Answer only if useful for recap or trap correction
- Do NOT force 3M/5M questions unless the actual PYQ pool contains such patterns.
- Do NOT force programming or HOTS homework unless the actual PYQ pool supports it.
- Every homework question must map to one concept/trap from Sections 3, 4, or 7.
- Homework questions should be self-generated, not copied actual PYQs.
Dynamic rule: if actual PYQs are only 1M/2M, homework stays mostly 1M/2M; if they include 3M/5M
programming, homework may include 3M/5M programming; never force unsupported marks or question types.
EVERY answer must be wrapped in &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;...&lt;/details&gt;.]

<h2 id="s10">10. 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="s11">11. 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 FOR COMBINED THEORY + PYQ:
- Output ONLY the HTML document starting with &lt;!DOCTYPE html&gt;.
- Do NOT wrap the output in markdown code fences.
- Use ONLY content from the lecture topic ("Built-in modules and library functions").
- Do NOT include content from other topics.
- Sections 1-6 are theory/concept sections:
    * Do not print actual PYQs in Sections 1-6.
    * Do not show year labels, paper metadata, or actual board question text in Sections 1-6.
- Section 7 is the PYQ Discussion section:
    * Actual PYQs are allowed and required.
    * Include year, marks, type, full question text, concept tested, model answer, marking point, and common mistake.
    * If source pool has 15 or fewer PYQs, include all actual PYQs.
- Sections 8-11 are revision/application sections:
    * Do not introduce new actual PYQs outside Section 7.
    * These sections may refer to "exam tips" and "common mistakes", but should not repeat full PYQ text.
- Never fabricate board years, marks, sections, paper names, or question text.
- Representative questions must not be labelled as actual board questions.
- Always finish the document completely through &lt;/html&gt;. If the answer is getting long, keep Sections 3 and 7 complete, then compact Sections 8-11 instead of truncating.

ANSWER HIDING RULES:
- Section 3 concept checks: every answer hidden inside &lt;details&gt;.
- Section 6 classroom practice: every answer hidden inside &lt;details&gt; (MCQ options listed WITHOUT .correct/.wrong before details).
- Section 7 PYQ Discussion: model answer, marking point, and common mistake hidden inside &lt;details&gt;.
- Section 8 self-check questions: every answer hidden inside &lt;details&gt;.
- Section 9 homework: every answer hidden inside &lt;details&gt;.
- In Section 7, question text, year, marks, type, and concept tested may stay visible.
- The beforeprint JS must auto-open all &lt;details&gt; for printing; never remove or skip this feature.

COMBINED THEORY + PYQ STRUCTURE RULE:
- Sections 1-6 teach the concept and prepare students.
- Section 7 is a visible PYQ Discussion / Board Questions section.
- Sections 8-11 provide compact revision, homework, tips, and cards.
- Actual PYQs must appear only in Section 7.
- Theory and revision sections must stay concept-focused and not dump board questions.

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.

BOX / CLASS USAGE RULES FOR COMBINED MODE:
- Do NOT use .pyq-box or .pyq-meta in Sections 1-6 or Sections 8-11.
- Use .pyq-box and .pyq-meta ONLY in Section 7: PYQ Discussion / Board Questions.
- 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.