Python Operators, Precedence, Type Conversion and Input/Output Class 11

Understand Python Operators, Precedence, Type Conversion, input() and print()

Python Operators, Precedence, Type Conversion, input() and print(): key facts

Precedence

• •Brackets
• •power (double star)
• •unary minus
• •multiply, divide, floor divide, modulus
• •+ -
• •comparisons
• •not
• •and
• •or

High to low.

Floor division and remainder

• •a // b rounds down
• •a % b has the sign of b
• •a = (a // b) x b + a % b

-7 // 2 = -4; -7 % 3 = 2.

Conversions

• •int() truncates
• •float() adds .0
• •str() makes text
• •input() returns text
• •bool of empty string, zero, None is False

Explicit type casting.

print options

• •sep sets the separator
• •end sets what follows
• •Default sep is a space
• •Default end is a new line

print("a", "b", sep="-") gives a-b.

How to answer Python Operators, Precedence, Type Conversion, input() and print() questions

1. 1Mark operators by precedence; handle brackets first.
2. 2Handle ** from the right; * / // % left to right.
3. 3For // and % with negatives, use the floor rule and verify with a = (a // b) x b + a % b.
4. 4Note the type of each result (/ always gives float).
5. 5For input(), convert before arithmetic; for print, apply sep and end exactly.

Python Operators, Precedence, Type Conversion, input() and print() 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 Python Operators, Precedence, Type Conversion, input() and print()

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

• // floors, % follows the divisor

  Floor division rounds down; the remainder takes the divisor's sign.

  Use it when: Negative numbers.

• input is text

  Always convert before arithmetic.

  Use it when: input().

Python Operators, Precedence, Type Conversion, input() and print(): solved examples

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

print(int("12") + 3)
print(str(5) + "5")
print(int(-7.9))
print(bool("0"), bool(0))
print("ab" * 3)

print("a", "b", sep="-")
print("x", end="!")
print("y")
print(not True or True, 5 > 3 > 1)

Where students lose marks in Python Operators, Precedence, Type Conversion, input() and print()

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

• ✗Mistake: Using / for whole-number division

  Expecting an integer from /.

  Wrong working

  10 / 2 = 5

  Right working

  10 / 2 = 5.0; 10 // 2 = 5

  ✓Do this: / always gives float.

  Usually costs: 1 mark

• ✗Mistake: Not converting input()

  Adding strings.

  Wrong working

  a = input(); a + 1

  Right working

  a = int(input()); a + 1

  ✓Do this: input() returns a string.

  Usually costs: 1 mark

• ✗Mistake: Left-to-right evaluation of **

  Treating ** as left-associative.

  Wrong working

  2 3 2 = 64

  Right working

  2 3 2 = 512

  ✓Do this: ** is right-associative.

  Usually costs: 1 mark

Practice questions on Python Operators, Precedence, Type Conversion, input() and print()

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

   What is the output of print(7 % 3, 7 // 3)?
   (a) 2 1
   (b) 1 2
   (c) 1 2.33
   (d) 2.33 1

   Hint

   Remainder first.

   Answer

   (b) 1 2

2. Q2 · 3 marks · Short answerHarder board level

   Evaluate: (i) -7 % 3; (ii) 15 // 4 + 15 % 4; (iii) 2 ** -1. (3 marks)

   Hint

   -7 = (-3) x 3 + 2.

   Answer

   (i) 2. (ii) 3 + 3 = 6. (iii) 2 ** -1 = 0.5.

3. Q3 · 3 marks · Short answerHarder board level

   What is the output?

   x = 5
   x += 2
   x *= 3
   x //= 4
   x **= 2
   print(x)

   (3 marks)

   Hint

   Step by step.

   Answer

   x = 5; x = 7; x = 21; x = 21 // 4 = 5; x = 5 ** 2 = 25. Output: 25.

4. Q4 · 1 mark · Assertion-reasonHarder board level

   Assertion (A): The expression "5" + "3" gives 53.
   Reason (R): The + operator concatenates two strings.
   (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

   String +.

   Answer

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

5. Q5 · 5 marks · Short answerHOTS / competency

   A program reads two marks and prints their average:

   a = input("First: ")
   b = input("Second: ")
   print((a + b) / 2)

   For inputs 40 and 60 explain what happens and rewrite the program correctly. What is the corrected output? (5 marks)

   Hint

   Strings are concatenated.

   Answer

   a and b are strings, so a + b is "4060" and "4060" / 2 raises a TypeError. Corrected: a = int(input("First: ")); b = int(input("Second: ")); print((a + b) / 2). For 40 and 60 the output is 50.0.

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.Result type of 10 / 2?Show answer

   float (5.0).

2. 2.Value of -7 // 2?Show answer

   -4.

3. 3.Value of 2 3 2?Show answer

   512.

4. 4.What does input() return?Show answer

   A string.

5. 5.Default end of print?Show answer

   A new line.

Python Operators, Precedence, Type Conversion, input() and print(): frequently asked questions