Assignment and augmented assignment in Python

Introduction

Assignment lets you store values in a name (variable). Augmented assignment helps update that value quickly.

When you want to save a number or text to use later.

When you want to add or subtract from a value you already have.

When you want to multiply or divide a value and keep the result.

When you want to update a variable without writing it twice.

Syntax

Python

variable = value
variable += value
variable -= value
variable *= value
variable /= value

Use = to assign a value to a variable.

Use augmented assignment like += to update the variable by combining assignment and operation.

Examples

Assign 5 to variable x.

Python

x = 5

Add 3 to x and save the result back to x.

Python

x += 3

Subtract 2 from x and save the result back to x.

Python

x -= 2

Multiply x by 4 and save the result back to x.

Python

x *= 4

Sample Program

This program shows how to assign a value to x and then update it using augmented assignments step by step.

Python

x = 10
print(f"Start: x = {x}")
x += 5
print(f"After adding 5: x = {x}")
x -= 3
print(f"After subtracting 3: x = {x}")
x *= 2
print(f"After multiplying by 2: x = {x}")
x /= 4
print(f"After dividing by 4: x = {x}")

Important Notes

Augmented assignment is shorter and easier to read than writing variable = variable + value.

Augmented assignment works with many operators like +=, -=, *=, /=, and more.

When dividing with /=, the result becomes a float even if both numbers are integers.

Summary

Use = to store values in variables.

Use augmented assignment like += to update variables quickly.

Augmented assignment makes code shorter and clearer.

Practice

1.

What does the += operator do in Python?

easy

A. Adds the right value to the left variable and updates it

B. Assigns a new variable without changing the old one

C. Subtracts the right value from the left variable

D. Creates a new list from two variables

Solution

1. Step 1: Understand the meaning of +=

   The += operator adds the value on the right to the variable on the left.

2. Step 2: Recognize it updates the variable

   It changes the original variable by adding the new value to it.

3. Final Answer:

   Adds the right value to the left variable and updates it -> Option A

4. Quick Check:

   += means add and assign [OK]

Hint: Think: add then store back in same variable [OK]

Common Mistakes:

• Confusing += with simple assignment =
• Thinking += creates a new variable
• Mixing += with subtraction or multiplication

2.

Which of the following is the correct syntax to add 5 to variable x using augmented assignment?

x = 10
# Add 5 to x here

easy

A. x =+ 5

B. x += 5

C. x =+5

D. x = x +

Solution

1. Step 1: Identify correct augmented assignment syntax

   The correct syntax to add and assign is x += 5.

2. Step 2: Check other options for syntax errors

   Choices like x =+ 5 and x =+5 use incorrect operator placement; x = x + is incomplete.

3. Final Answer:

   x += 5 -> Option B

4. Quick Check:

   Use += for adding and assigning [OK]

Hint: Remember: operator before equals for augmented assignment [OK]

Common Mistakes:

• Writing =+ instead of +=
• Leaving out the value after +
• Using incomplete expressions

3.

What is the output of this code?

count = 3
count += 4
count -= 2
print(count)

medium

A. 9

B. 7

C. 3

D. 5

Solution

1. Step 1: Calculate count += 4

   Starting from 3, adding 4 gives 7.

2. Step 2: Calculate count -= 2

   Subtracting 2 from 7 gives 5.

3. Final Answer:

   5 -> Option D

4. Quick Check:

   3 + 4 - 2 = 5 [OK]

Hint: Follow each operation step-by-step [OK]

Common Mistakes:

• Adding and subtracting in wrong order
• Confusing += and -= effects
• Ignoring the initial value

4.

Find the error in this code snippet:

total = 10
total + = 5
print(total)

medium

A. TypeError because + cannot be used with int

B. NameError because total is not defined

C. SyntaxError due to space in augmented assignment

D. No error, prints 15

Solution

1. Step 1: Check augmented assignment syntax

   The operator += must not have spaces between + and =.

2. Step 2: Identify the error caused by space

   Writing + = causes a SyntaxError in Python.

3. Final Answer:

   SyntaxError due to space in augmented assignment -> Option C

4. Quick Check:

   No spaces allowed in += operator [OK]

Hint: No spaces between + and = in augmented assignment [OK]

Common Mistakes:

• Adding spaces inside augmented assignment operator
• Assuming it works like normal addition
• Ignoring syntax error messages

5.

You have a variable score = 50. You want to increase it by 10%, then subtract 5 using augmented assignments. Which code correctly does this?

score = 50
# Increase by 10%
# Subtract 5

hard

A. score *= 1.1
score -= 5

B. score += 10
score -= 5

C. score = score + 10%
score = score - 5

D. score += 0.1
score -= 5

Solution

1. Step 1: Increase score by 10%

   Multiplying by 1.1 increases the value by 10%, so score *= 1.1 is correct.

2. Step 2: Subtract 5 using augmented assignment

   Use score -= 5 to subtract 5 from the updated score.

3. Final Answer:

   score *= 1.1 score -= 5 -> Option A

4. Quick Check:

   Multiply by 1.1 then subtract 5 [OK]

Hint: Use *= for percent increase, then -= for subtraction [OK]

Common Mistakes:

• Adding 10 instead of 10%
• Using invalid syntax like 10%
• Not updating score before subtracting