Operator precedence and evaluation order in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the correct result using operator precedence.

Python

result = 3 + 4 * [1]

Drag options to blanks, or click blank then click option'

A1

B2

C5

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Adding 3 + 4 first, then multiplying by the number.

Multiplication (*) has higher precedence than addition (+), so 4 * 5 is calculated first, then 3 is added.

2fill in blank

medium

Complete the code to get the correct boolean result using operator precedence.

Python

result = True or False and [1]

Drag options to blanks, or click blank then click option'

ATrue

B0

CNone

DFalse

Attempts:

3 left

💡 Hint

Common Mistakes

Evaluating True or False first.

In Python, and has higher precedence than or, so False and False is evaluated first, resulting in False. Then True or False is True.

3fill in blank

hard

Fix the error in the expression to get the correct result.

Python

result = (10 - 3) [1] 2 ** 3

Drag options to blanks, or click blank then click option'

A*

B-

C+

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using + or - instead of * changes the result.

Exponentiation (**) has higher precedence than multiplication (*), so 2 ** 3 is calculated first, then multiplied by (10 - 3).

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that includes only even squares.

Python

squares = {x: x[1]2 for x in range(1, 6) if x [2] 2 == 0}

Drag options to blanks, or click blank then click option'

A**

B%

C//

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using // instead of % for checking even numbers.

The ** operator is used for exponentiation to square the number. The modulo operator % checks if the number is even by testing if the remainder when divided by 2 is zero.

5fill in blank

hard

Fill all three blanks to create a filtered dictionary with uppercase keys and values greater than zero.

Python

result = [1]: [2] for [3], v in data.items() if v > 0}

Drag options to blanks, or click blank then click option'

Ak.upper()

Bv

Ck

Ditem

Attempts:

3 left

💡 Hint

Common Mistakes

Using item instead of k as the loop variable.

The key k is converted to uppercase with k.upper(). The value v is used as the dictionary value. The loop variable for keys is k.

Practice

1. Which operator has the highest precedence in the expression 3 + 4 * 2?

easy

A. Multiplication (*)

B. Addition (+)

C. Subtraction (-)

D. Division (/)

Solution

1. Step 1: Recall operator precedence rules

   Multiplication (*) has higher precedence than addition (+), subtraction (-), and division (/).

2. Step 2: Identify highest precedence operator in expression

   In 3 + 4 * 2, multiplication (*) runs before addition (+).

3. Final Answer:

   Multiplication (*) -> Option A

4. Quick Check:

   Highest precedence = Multiplication (*) [OK]

Hint: Multiplication and division run before addition and subtraction [OK]

Common Mistakes:

• Thinking addition runs before multiplication
• Ignoring operator precedence
• Assuming left to right always applies

2. Which of the following expressions is syntactically correct in Python?

easy

A. 5 + * 3

B. 4 + (3 * 2)

C. 7 / / 2

D. 8 - -

Solution

1. Step 1: Check each expression for syntax errors

   5 + * 3 has two operators in a row without operand: invalid.
   4 + (3 * 2) uses parentheses correctly and valid operators.
   7 / / 2 has double division operator which is invalid.
   8 - - ends with operator without operand: invalid.

2. Step 2: Confirm correct syntax

   Only 4 + (3 * 2) is syntactically correct: 4 + (3 * 2).

3. Final Answer:

   4 + (3 * 2) -> Option B

4. Quick Check:

   Valid syntax = 4 + (3 * 2) [OK]

Hint: Check for missing operands or extra operators [OK]

Common Mistakes:

• Using two operators in a row
• Missing parentheses around expressions
• Ending expression with an operator

3. What is the output of the following code?

result = 10 - 3 * 2 + 4 // 2
print(result)

medium

A. 5

B. 8

C. 6

D. 4

Solution

1. Step 1: Apply operator precedence and evaluate multiplication and floor division first

   3 * 2 = 6
   4 // 2 = 2

2. Step 2: Evaluate the expression left to right with addition and subtraction

   10 - 6 + 2 = 4 + 2 = 6

3. Final Answer:

   6 -> Option C

4. Quick Check:

   10 - 6 + 2 = 6 [OK]

Hint: Multiply and divide before add and subtract [OK]

Common Mistakes:

• Adding before multiplying
• Using normal division instead of floor division
• Ignoring left to right evaluation for same precedence

4. Find the error in this expression:

value = 5 + (3 * 2

medium

A. No error, expression is correct

B. Wrong operator used

C. Extra operator before 2

D. Missing closing parenthesis

Solution

1. Step 1: Check parentheses balance

   Expression has an opening parenthesis '(' but no matching closing parenthesis ')'.

2. Step 2: Identify syntax error

   Missing closing parenthesis causes syntax error in Python.

3. Final Answer:

   Missing closing parenthesis -> Option D

4. Quick Check:

   Parentheses must be balanced [OK]

Hint: Count opening and closing parentheses carefully [OK]

Common Mistakes:

• Ignoring missing parentheses
• Assuming expression is valid without closing parenthesis
• Confusing operator errors with syntax errors

5. Given the expression result = (2 + 3) * (4 - 1) ** 2 // 5, what is the value of result?

hard

A. 9

B. 15

C. 5

D. 25

Solution

1. Step 1: Evaluate parentheses and exponentiation first

   (2 + 3) = 5
   (4 - 1) = 3
   3 ** 2 = 9

2. Step 2: Multiply and then floor divide

   5 * 9 = 45
   45 // 5 = 9

3. Final Answer:

   9 -> Option A

4. Quick Check:

   Parentheses and exponent first, then multiply, then floor divide [OK]

Hint: Do parentheses and powers before multiply/divide [OK]

Common Mistakes:

• Ignoring exponentiation precedence
• Dividing before multiplying
• Not applying floor division correctly