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: "Dictionary operations"
Lecture number 13 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 "Dictionary operations" only.
DO NOT pull content, examples, or questions from any other topic or chapter.

LECTURE MODE: SUBTOPIC PYQ PRACTICE
- Scope: "Dictionary operations" only.
- Do not reteach the topic from scratch. Use a short recap only when a PYQ needs it.
- Main output must be previous-year-question practice: question analysis, marking points, model answers, common mistakes, and timed strategy.
- Use the 29 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: Dictionary operations PYQ
Subtopics to cover today:
- Dictionary 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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Dictionary operations PYQ

PYQ PRACTICE SCOPE: Dictionary operations.
Concept ID: U1_DICTIONARY_OPS.
Use only previous-year questions whose concept_ids include U1_DICTIONARY_OPS.

Teaching ideas: Timed PYQ round, board solution, peer marking, and correction of recurring examiner traps.

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

| Year | Questions | Marks |
|------|-----------|-------|
| 2021 | 1 | 1 |
| 2022 | 2 | 3 |
| 2023 | 7 | 9 |
| 2024 | 3 | 5 |
| 2025 | 10 | 11 |
| 2026 | 6 | 6 |
| **Total** | **29** | **35** |

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SECTION 4: ACTUAL PREVIOUS YEAR QUESTIONS
(Scope: "Dictionary operations" only — 29 questions from board papers)
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PYQ LECTURE RULE: use these questions as the source pool for practice.
- Cover every concept tested across the full PYQ pool.
- Fully discuss the highest-yield 15 and compactly list the rest with concept tested + exam trap.
- Compression and representative questions are allowed only for repeated patterns beyond the fully discussed 15.
- Do not fabricate board years, marks, sections, or questions.
- Representative questions must never be labelled as real board questions.


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

Q1. [MCQ] [1M] [Easy] Section-A
Which of these about a dictionary is false?
a) The values of a dictionary can be accessed using keys
b) The keys of a dictionary can be accessed using values
c) Dictionaries aren't ordered
d) Dictionaries are mutable

--- 2022 Board Exam (2 questions | 3 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
Given the following dictionaries:
dict_exam={"Exam":"AISSCE", "Year":2023}
dict_result={"Total":500, "Pass_Marks":165}
Which statement will merge the contents of both dictionaries?
a) dict_exam.update(dict_result)
b) dict_exam + dict_result
c) dict_exam.add(dict_result)
d) dict_exam.merge(dict_result)

Q2. [Output Prediction] [2M] [Easy] Section-B
(a) Given is a Python string declaration:
myexam="@@CBSE Examination 2022@@"
Write the output of: print(myexam[::-2])
(b) Write the output of the code given below:
my_dict = {"name": "Aman", "age": 26}
my_dict['age'] = 27
my_dict['address'] = "Delhi"
print(my_dict.items())

--- 2023 Board Exam (7 questions | 9 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
Which of the following statement(s) would give an error after executing the following code ?
Stud={"Murugan":100, "Mithu":95} # Statement 1
print (Stud[95]) # Statement 2
Stud ["Murugan"]=99 # Statement 3
print (Stud.pop() ) # Statement 4
print (Stud) # Statement 5
(a) Statement 2
(b) Statement 3
(c) Statement 4
(d) Statements 2 and 4

Q2. [MCQ] [1M] [Easy] Section-A
Which of the following is not a sequential datatype in Python ?
(a) Dictionary
(b) String
(c) List
(d) Tuple

Q3. [MCQ] [1M] [Easy] Section-A
Given the following dictionary
Day={1:"Monday", 2: "Tuesday", 3: "Wednesday" }
Which statement will return "Tuesday".
(a) Day.pop()
(b) Day.pop(2)
(c) Day.pop(1)
(d) Day.pop("Tuesday")

Q4. [MCQ] [1M] [Easy] Section-A
Which of the following functions is a valid built-in function for both list and dictionary datatype ?
(a) items()
(b) len()
(c) update()
(d) values()

Q5. [MCQ] [1M] [Easy] Section-A
Which of the following will delete key-value pair for key = "Red" from a dictionary D1?
a) delete D1("Red")
b) del D1["Red"]
c) del.D1["Red"]
d) D1.del["Red"]

Q6. [Output Prediction] [2M] [Easy] Section-B
(a) Given is a Python string declaration :
NAME = "Learning Python is Fun"
Write the output of : print (NAME [-5:-10:-1])

(b) Write the output of the code given below :
dict1={1: ["Rohit",20], 2: ["Siya",90]}
dict2={1: ["Rahul",95], 5: ["Rajan",80]}
dict1.update (dict2)
print (dict1.values())

Q7. [Output Prediction] [2M] [Easy] Section-B
Predict the output of the following code:
S = "LOST"
L = [10,21,33,4]
D={}
for I in range(len(S)):
    if I%2==0:
        D[L.pop()] = S[I]
    else:
        D[L.pop()] = I+3
for K,V in D.items():
    print(K,V,sep="*")

--- 2024 Board Exam (3 questions | 5 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
If my_dict is a dictionary as defined below, then which of the following statements will raise an exception?
my_dict = {'apple': 10, 'banana': 20, 'orange': 30}
a) my_dict.get('orange')
b) print(my_dict['apple', 'banana'])
c) my_dict['apple']=20
d) print(str(my_dict))

Q2. [Output Prediction] [2M] [Easy] Section-B
Predict the output of the following code :
d={"IND":"DEL","SRI":"COL","CHI":"BEI"}
str1=""
for i in d:
    str1=str1+str(d[i])+"@"
str2=str1[:-1]
print (str2)

Q3. [Short Answer] [2M] [Easy] Section-B
(b) A dictionary dict2 is copied into the dictionary dict1 such that the common key's value gets updated. Write the Python commands to do the task and after that empty the dictionary dict1.

--- 2025 Board Exam (10 questions | 11 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
Consider the statements given below and then choose the correct output from the given options:
D={'S01':95, 'S02':96}
for I in D:
    print(I,end='#')
(A) S01#S02#
(B) 95#96#
(C) s01,95#S02,96#
(D) S01#95#S02#96#

Q2. [MCQ] [1M] [Easy] Section-A
Which of the following built-in function/method returns a dictionary?
(A) dict()
(B) keys()
(C) values()
(D) items()

Q3. [MCQ] [1M] [Easy] Section-A
Which of the following is a mapped data type ?
(A) List
(B) Sets
(C) Dictionary
(D) Boolean

Q4. [MCQ] [1M] [Easy] Section-A
If the dictionary D1 is defined as :
D1={1:'a',2:'b'}
then which of the following statements is incorrect and hence will result in an error ?
(A) D1.get(1)
(B) D1.get(3)
(C) D1.del(1)
(D) D1.clear()

Q5. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 and D2 are Python dictionaries, write the required statement using built-in functions/methods.
Delete all the elements of D1.

Q6. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 and D2 are Python dictionaries, write the required statement using built-in functions/methods.
Generate a list of values of D1.

Q7. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 and D2 are Python dictionaries, write the required statement using built-in functions/methods.
Update dictionary D2 with the elements of D1.

Q8. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 and D2 are Python dictionaries, write the required statement using built-in functions/methods.
Generate a tuple of keys of D2.

Q9. [MCQ] [1M] [Easy] Section-A
What will be the output of the following Python code?
my_dict = {"name": "Alicia", "age": 27, "city": "DELHI"}
print(my_dict.get("profession", "Not Specified"))
a) Alicia
b) DELHI
c) None
d) Not Specified

Q10. [Output Prediction] [2M] [Easy] Section-B
Predict the output of the Python code given below:
emp = {"Arv": (85000,90000),"Ria": (78000,88000),"Jay": (72000,80000),"Tia": (80000,70000)}
selected = [ ]
for name in emp:
    salary = emp[name]
    average = (salary[0] + salary[1]) / 2
    if average > 80000:
        selected.append(name)
print(selected)

--- 2026 Board Exam (6 questions | 6 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
Which of the following statements is true about dictionaries in Python ?
(A) A dictionary is an example of sequence datatype.
(B) A dictionary cannot have two elements with same key.
(C) A dictionary cannot have two elements with same value.
(D) The key and value of an element cannot be the same.

Q2. [MCQ] [1M] [Easy] Section-A
If L is a list with 6 elements, then which of the following statements will raise an exception ?
(A) L.pop(1)
(B) L.pop(6)
(C) L.insert(1,6)
(D) L.insert(6,1)

Q3. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 is a dictionary in Python, write the required Python expression/statement.
Write a Python expression to check if the key, 'RNo' is present in D1.

Q4. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 is a dictionary in Python, write the required Python expression/statement.
Write a Python expression to check if any key in D1 has a value 12.

Q5. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 is a dictionary in Python, write the required Python expression/statement.
Write a single statement using a built-in function to add the key:value pair 'RNo':12 if the key 'RNo' is not present in D1. If the key is present, the function should return its value.

Q6. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 is a dictionary in Python, write the required Python expression/statement.
Write a single statement to delete all the elements from D1.

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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: Dictionary operations
  Pattern: MCQ=15, Output Prediction=5, Short Answer=9 | Marks: 1M=23, 2M=6 | Total: 29 questions
  [MCQ] [1M] [Easy] × 11
    → Core concept of Dictionary operations
  [Output Prediction] [2M] [Easy] × 5
    → Output/result interpretation for the current concept
  [MCQ] [1M] [Easy] × 2
    → Raising and handling exceptions
  [Short Answer] [2M] [Easy]
    → Core concept of Dictionary operations
  [MCQ] [1M] [Easy] × 2
    → Output/result interpretation for the current concept
  [Short Answer] [1M] [Easy] × 8
    → Core concept of Dictionary operations


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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 | Dictionary operations | 113 | 29 | 35M | 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 previous-year questions to identify traps, marking points, and common mistakes. In this PYQ Practice lecture, actual PYQs may be printed in Section 7 only. Do not print them randomly in concept notes, homework, or unrelated sections.

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

No static trap list exists yet for "Dictionary operations". Self-generate 4–7 traps from:
- actual question patterns for Dictionary 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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<!-- 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">Dictionary operations PYQ — Lecture 13</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 what the PYQs above test — use &lt;ul&gt;&lt;li&gt;]

<h2 id="s2">2. 35-Minute Lecture Flow</h2>
[HTML table: Time | Activity | Teacher Action — include a PYQ discussion with full + compressed coverage]

<h2 id="s3">3. Quick Concept Recap</h2>
[Keep this section short. Do NOT reteach the full topic from scratch.
Include only the rules needed to solve the PYQs — i.e. the traps listed in the
EXAMINER FINGERPRINT section above (for this lecture: Dictionary operations).
Use .def-box and .key-box only. Add at most one tiny example if needed.
Do not include long theory, long programming tasks, or unrelated examples.]

<h2 id="s4">4. Examiner Tricks &amp; Common Mistakes</h2>
[One .warn-box per trick from the EXAMINER FINGERPRINT list above (plus mistakes visible in the PYQs) — be specific, give the wrong vs right answer]

<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>
[Modelled on PYQ 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.

Practice questions must follow the difficulty and mark pattern of the actual PYQ pool.

For this topic:
* 3×1M MCQ
* 5×1M/2M Short Answer
* No 3–5M programming question (the actual PYQ pool contains no such pattern)
* No HOTS question (the provided PYQs do not reveal a higher-order trap)

Every question must be based on one of the traps from Section 4 (EXAMINER FINGERPRINT).
Every answer must be hidden inside &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;...&lt;/details&gt;.

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;
(Note: options list shown WITHOUT .correct/.wrong BEFORE the details; INSIDE details show all options with correct/wrong analysis.)

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;

Dynamic distribution rule:
* If actual PYQs are only 1M/2M, keep generated practice mostly 1M/2M.
* If actual PYQs include 3M/5M programming, include 3M/5M programming practice.
* Never force HOTS or programming questions when the provided PYQ pool does not support them.]

<h2 id="s7">7. PYQ Discussion / Full + Compressed Coverage (29 source questions)</h2>
[This source pool has 29 actual PYQs.
PYQ COVERAGE RULE:
  - If the PYQ pool has 15 or fewer questions, include and discuss ALL actual PYQs in Section 7.
  - Do not compress, replace, paraphrase, or skip any actual PYQ in a small pool.
  - This pool has more than 15 questions: fully discuss the highest-yield 15 and compactly
    list the rest with concept tested + exam trap.
  - Compression is allowed only when the source pool has more than 15 questions.
  - Never fabricate board years, marks, sections, or question text.
For every fully discussed actual PYQ include:
  year · marks · type · full question text · concept tested · model answer inside &lt;details&gt; · common mistake inside &lt;details&gt;
Order questions Easy to Tough; within difficulty, order 1 mark → 2 marks → 3 marks → 4/5 marks.
Use this structure for actual PYQ examples:
  Use this structure for each question:
  &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 question text — include code if any]&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; [full answer with code/table as needed, using .kw/.bi/.st token spans in &lt;pre&gt;&lt;code&gt;]&lt;br&gt;
      &lt;b&gt;Common mistake:&lt;/b&gt; [what students get wrong — be specific]
    &lt;/details&gt;
  &lt;/div&gt;

For compressed representative questions, label them "Representative PYQ-pattern question", not as a real board question, and never show a fake year, marks, or section.]

<h2 id="s8">8. Student Notes (Copy-ready)</h2>
[Concise notes — every concept from PYQs — 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 PYQ pattern for this topic:
- 3×1M MCQ
- 3×1M Short 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 trap or pattern from Section 4 / Section 7.
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; inside .self-test-box or .mcq-box.]

<h2 id="s10">10. Exam Tips</h2>
[5 specific tips as .tip-box — derived from PYQ patterns for THIS topic only]

<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:
- Output ONLY the HTML document starting with &lt;!DOCTYPE html&gt;
- Do NOT wrap in markdown code fences
- Do NOT add explanatory text outside the HTML
- Use ONLY content from "Dictionary operations" — zero content from other topics
- PYQ lecture: fully discuss the highest-yield 15 and compactly list the rest with concept tested + exam trap; compression is allowed only because this pool exceeds 15
- 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.
- If 15 or fewer PYQs are provided, include ALL actual PYQs in Section 7.
- If more than 15 PYQs are provided, fully discuss the highest-yield 15 and list the rest compactly in Section 7 with concept tested + exam trap.
- ANSWER HIDING (most important for student use):
    * Section 6 MCQs: options listed WITHOUT .correct/.wrong BEFORE details; full analysis only INSIDE &lt;details&gt;
    * Section 6 short-answer questions: EVERY answer in &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;...&lt;/details&gt;
    * Do not mention programming/HOTS in Section 6 answer-hiding rules unless Section 6 actually includes programming/HOTS based on the source PYQ pool.
    * Section 8 self-check and Section 9 homework: EVERY answer in &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;
    * Section 7 PYQ Discussion / Full + Compressed Coverage: model answer + common mistake inside &lt;details&gt;&lt;summary&gt;▶ View Model Answer&lt;/summary&gt;
    * .pyq-box question text and concept tested stay visible outside &lt;details&gt;; only Model Answer + Common mistake are hidden inside &lt;details&gt;
    * The beforeprint JS already auto-opens all &lt;details&gt; for printing — never skip this feature
- INLINE CODE SIZE RULE:
    * Inline code (function/method names and short snippets relevant to "Dictionary operations") 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: this is a PYQ lecture, so .pyq-box/.pyq-meta are used as shown in Section 7 above (never in theory lectures).
- All content goes inside &lt;div class="main-content"&gt;
- The &lt;nav class="toc-sidebar"&gt; is already in the template — JS auto-builds TOC links
- Print buttons (.print-bar), including Read Mode, are in the template — DO NOT add them again; they auto-hide on print
- Include the full CSS and JS exactly as given (the CODE CSS already follows the INLINE CODE SIZE RULE above).