abs() and round() in Python - Mini Project: Build & Apply

Using abs() and round() in Python

📖 Scenario: You are working on a simple weather app that shows temperature differences and rounded temperatures for easy reading.

🎯 Goal: Build a small program that calculates the absolute difference between two temperatures and rounds a temperature value to the nearest whole number.

📋 What You'll Learn

Create variables with exact temperature values

Use the abs() function to find the absolute difference

Use the round() function to round a temperature

Print the results exactly as instructed

💡 Why This Matters

🌍 Real World

Weather apps often show temperature differences and rounded temperatures to help users understand the weather easily.

💼 Career

Knowing how to use abs() and round() is useful in data processing, financial calculations, and any job involving numbers.

1

Create temperature variables

Create two variables called temp_morning and temp_evening with the values -3.7 and 5.2 respectively.

Python

# Create variables temp_morning and temp_evening with values -3.7 and 5.2
# Your code here

Hint

Use the assignment operator = to set the values.

2

Calculate absolute temperature difference

Create a variable called temp_diff and set it to the absolute difference between temp_evening and temp_morning using the abs() function.

Python

temp_morning = -3.7
temp_evening = 5.2
# Calculate absolute difference using abs()
# Your code here

Hint

Use abs() around the subtraction to get a positive result.

3

Round the morning temperature

Create a variable called rounded_morning and set it to the value of temp_morning rounded to the nearest whole number using the round() function.

Python

temp_morning = -3.7
temp_evening = 5.2
temp_diff = abs(temp_evening - temp_morning)
# Round temp_morning using round()
# Your code here

Hint

Use round() with the variable inside the parentheses.

4

Print the results

Print the values of temp_diff and rounded_morning exactly as shown below, each on its own line:
Absolute difference: 8.9
Rounded morning temperature: -4

Python

temp_morning = -3.7
temp_evening = 5.2
temp_diff = abs(temp_evening - temp_morning)
rounded_morning = round(temp_morning)
# Print the results
# Your code here

Hint

Use print() with f-strings to show the variable values.

Practice

1. What does the Python function abs() do when given a number?

easy

A. Rounds the number to the nearest integer

B. Returns the negative of the number

C. Converts the number to a string

D. Returns the positive distance of the number from zero

Solution

1. Step 1: Understand the purpose of abs()

   The abs() function returns how far a number is from zero without considering its sign.

2. Step 2: Compare with other options

   Rounding, string conversion, or negation are different functions; only abs() returns the positive distance.

3. Final Answer:

   Returns the positive distance of the number from zero -> Option D

4. Quick Check:

   abs(-5) = 5 [OK]

Hint: Think: absolute means distance without sign [OK]

Common Mistakes:

• Confusing abs() with round()
• Thinking abs() changes the number's sign
• Assuming abs() converts to string

2. Which of the following is the correct way to round the number 3.14159 to 2 decimal places in Python?

easy

A. round(3.14159, '2')

B. round(3.14159.2)

C. round(3.14159, 2)

D. round(3.14159, 2.0)

Solution

1. Step 1: Check the syntax of round()

   The round() function takes a number and an integer for decimal places, like round(number, digits).

2. Step 2: Validate each option

   round(3.14159, 2) uses correct syntax with an integer 2. round(3.14159.2) has a dot instead of a comma. round(3.14159, '2') uses a string '2' which is invalid. round(3.14159, 2.0) uses a float 2.0 which is accepted as decimal places.

3. Final Answer:

   round(3.14159, 2) -> Option C

4. Quick Check:

   round(3.14159, 2) = 3.14 [OK]

Hint: Use comma and integer for decimals in round() [OK]

Common Mistakes:

• Using dot instead of comma between arguments
• Passing decimal places as string
• Passing decimal places as float

3. What is the output of this code?

print(abs(-7.8))
print(round(2.675, 2))

medium

A. 7.8 and 2.68

B. 7.8 and 2.67

C. -7.8 and 2.68

D. -7.8 and 2.67

Solution

1. Step 1: Calculate abs(-7.8)

   The absolute value of -7.8 is 7.8, so the first print outputs 7.8.

2. Step 2: Calculate round(2.675, 2)

   Due to floating-point rounding, 2.675 rounds to 2.67 (not 2.68) in Python.

3. Final Answer:

   7.8 and 2.67 -> Option B

4. Quick Check:

   abs(-7.8) = 7.8, round(2.675, 2) = 2.67 [OK]

Hint: Remember floating-point quirks in round() [OK]

Common Mistakes:

• Expecting round(2.675, 2) to be 2.68
• Forgetting abs() returns positive value
• Mixing signs in output

4. The following code has an error. What is it?

num = -4.5
print(round(abs(num), 1.0))

medium

A. round() decimal places must be an integer, not float

B. abs() cannot take negative numbers

C. print() syntax is incorrect

D. num variable is not defined

Solution

1. Step 1: Analyze abs(num)

   The abs() function works fine with negative numbers, so no error here.

2. Step 2: Check round() arguments

   The second argument to round() must be an integer, but 1.0 is a float, causing a TypeError.

3. Final Answer:

   round() decimal places must be an integer, not float -> Option A

4. Quick Check:

   round(..., 1.0) causes error [OK]

Hint: Decimal places in round() must be int, not float [OK]

Common Mistakes:

• Thinking abs() can't take negatives
• Passing float instead of int for decimals
• Assuming print() syntax error

5. You have a list of numbers: nums = [-3.1415, 2.718, -1.414, 0]. You want to create a new list with the absolute values rounded to 2 decimal places. Which code does this correctly?

hard

A. rounded = [round(abs(x), 2) for x in nums]

B. rounded = [round(x, 2) for x in nums]

C. rounded = [round(abs(x), '2') for x in nums]

D. rounded = [round(abs(x), 2.0) for x in nums]

Solution

1. Step 1: Understand the goal

   We want absolute values first, then round them to 2 decimals.

2. Step 2: Check each option

   rounded = [round(abs(x), 2) for x in nums] correctly applies abs() then round() with integer 2. rounded = [round(x, 2) for x in nums] rounds but does not apply abs(), leaving negative values negative. rounded = [round(abs(x), '2') for x in nums] uses string '2' which is invalid. rounded = [round(abs(x), 2.0) for x in nums] uses float 2.0 which is accepted as decimal places.

3. Final Answer:

   rounded = [round(abs(x), 2) for x in nums] -> Option A

4. Quick Check:

   abs then round with int decimals [OK]

Hint: Apply abs() before round() with integer decimals [OK]

Common Mistakes:

• Rounding before abs() changes results
• Using string or float for decimal places
• Confusing order of functions