Python Tuples Class 11: One-Item Tuples, Tuple Assignment, Nested Tuples and Programs

Understand Tuples: Immutability, Operations, Tuple Assignment and Programs (CBSE 11)

Tuples: Immutability, Operations, Tuple Assignment and Programs (CBSE 11): key facts

Making tuples

• •(5,) one item
• •(5) is an integer
• •t = 1, 2, 3 is a tuple
• •() is empty
• •tuple(seq) converts

The comma makes the tuple.

Tuple methods

• •count(x) occurrences
• •index(x) first position
• •no append, remove or sort

Only two methods exist.

Functions

• •len
• •min
• •max
• •sum
• •sorted(t) returns a list
• •tuple(sorted(t)) returns a tuple

sum needs numbers.

Tuple assignment

• •a, b = b, a swaps
• •right side is evaluated first
• •names on the left equal items on the right

a, b = b, a + b uses the old values.

How to answer Tuples: Immutability, Operations, Tuple Assignment and Programs (CBSE 11) questions

1. 1Check for the trailing comma before calling an expression a tuple.
2. 2Write each tuple with its indices before slicing.
3. 3For tuple assignment evaluate the whole right side using the old values, then assign left to right.
4. 4Remember that tuples cannot be modified, so look for TypeError in assignments such as t[i] = x.
5. 5Print sorted(t) as a list in square brackets and tuple(...) in round brackets.

Tuples: Immutability, Operations, Tuple Assignment and Programs (CBSE 11) in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Tricks to remember Tuples: Immutability, Operations, Tuple Assignment and Programs (CBSE 11)

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Comma makes the tuple

  Brackets are optional, the comma is not: (5,) is a tuple but (5) is not.

  Use it when: Type questions.

• Right first, then left

  In a, b = b, a + b the whole right side is worked out before assigning.

  Use it when: Swap and Fibonacci-style questions.

• Two methods only

  count and index are all a tuple has.

  Use it when: Theory MCQs.

Tuples: Immutability, Operations, Tuple Assignment and Programs (CBSE 11): solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

a, b = 3, 4
a, b = b, a
print(a, b)
a, b = b, a + b
print(a, b)

t = (1, [2, 3], "a")
t[1].append(4)
print(t)
t = t + (5,)
print(t, len(t))
t[2] = "b"

Where students lose marks in Tuples: Immutability, Operations, Tuple Assignment and Programs (CBSE 11)

The slips examiners see most often, and what to write instead.

• ✗Mistake: Forgetting the comma in a one-item tuple

  Believing the brackets create the tuple.

  Wrong working

  t = (5); len(t) raises TypeError

  Right working

  t = (5,); len(t) is 1

  ✓Do this: Add the trailing comma.

  Usually costs: 1 mark

• ✗Mistake: Trying to change a tuple item

  Treating a tuple like a list.

  Wrong working

  t[0] = 9

  Right working

  t = (9,) + t[1:]

  ✓Do this: Create a new tuple.

  Usually costs: 1 to 2 marks

• ✗Mistake: Writing the swap with the new values

  Working left to right instead of evaluating the right side first.

  Wrong working

  a, b = b, a + b with a = 3, b = 4 worked out as a = 4 and then b = a + b = 8

  Right working

  b = old a + old b = 3 + 4 = 7, so a = 4 and b = 7

  ✓Do this: Use old values on the right.

  Usually costs: 1 mark

Practice questions on Tuples: Immutability, Operations, Tuple Assignment and Programs (CBSE 11)

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQBoard level

   Which of these is a tuple with exactly one item?
   (a) (7)
   (b) [7]
   (c) (7,)
   (d) {7}

   Hint

   The comma.

   Answer

   (c) (7,)

2. Q2 · 1 mark · Assertion-reasonHarder board level

   Assertion (A): For t = (1, 2, 3), the statement t[0] = 9 raises an error.
   Reason (R): A tuple is an immutable sequence.
   (a) Both A and R are true, and R is the correct explanation of A.
   (b) Both A and R are true, but R is not the correct explanation of A.
   (c) A is true, but R is false.
   (d) A is false, but R is true.

   Hint

   Item assignment.

   Answer

   (a) Both A and R are true, and R is the correct explanation of A.

3. Q3 · 4 marks · Short answerHarder board level

   Give the output:

   t = (3, 1, 2)
   print(sorted(t), t, tuple(sorted(t)), t * 2, t + (0,))

   (4 marks)

   Hint

   sorted gives a list.

   Answer

   sorted(t) is the list [1, 2, 3]; t is unchanged (3, 1, 2); tuple(sorted(t)) is (1, 2, 3); t * 2 is (3, 1, 2, 3, 1, 2); t + (0,) is (3, 1, 2, 0). Output: [1, 2, 3] (3, 1, 2) (1, 2, 3) (3, 1, 2, 3, 1, 2) (3, 1, 2, 0)

4. Q4 · 5 marks · Short answerHarder board level

   Write a program for the tuple t = (2, 5, 2, 3, 5, 2) that prints each distinct value once, in the order of first appearance, with its frequency. Give the output. (5 marks)

   Hint

   Keep a list of values already seen.

   Answer

   seen = []; for x in t: if x not in seen: seen.append(x); print(x, t.count(x)). Output lines: 2 3, then 5 2, then 3 1.

5. Q5 · 5 marks · Short answerHOTS / competency

   Give the output of the program:

   t = ((1, 2), (3, 4, 5))
   print(len(t), t[1][2], t[0] + t[1], len(t[0] + t[1]))
   pairs = ((1, 2), (3, 4))
   for a, b in pairs:
       print(a * b)

   (5 marks)

   Hint

   Joining two tuples gives one longer tuple.

   Answer

   len(t) is 2 (two inner tuples); t[1][2] is 5; t[0] + t[1] is (1, 2, 3, 4, 5) with length 5. The loop unpacks each pair: 1 * 2 = 2 and 3 * 4 = 12. Output: 2 5 (1, 2, 3, 4, 5) 5, then 2, then 12.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.What makes a one-item tuple?Show answer

   A trailing comma, as in (5,).

2. 2.Name the two tuple methods.Show answer

   count() and index().

3. 3.What does sorted(t) return?Show answer

   A list.

4. 4.How do you swap a and b?Show answer

   a, b = b, a.

5. 5.Can a tuple hold a list?Show answer

   Yes, and that list can be changed in place.

Tuples: Immutability, Operations, Tuple Assignment and Programs (CBSE 11): frequently asked questions