The code takes an Air Quality Index (AQI) value from...

The code takes an Air Quality Index (AQI) value from the user and determines its classification based on the AQI scale, then displays a corresponding message. However, there is a logical error in the code that will lead to incorrect classifications for certain values. Here's a detailed explanation:

What the code intends to do:

1. Prompt the user to input an integer as the AQI.

2. Classify the AQI into one of six categories based on its range:

   • Good (0–50)
   • Moderate (51–100)
   • Unhealthy for Sensitive Groups (101–150)
   • Unhealthy (151–200)
   • Very Unhealthy (201–300)
   • Hazardous (above 300 or potentially below 0)

3. Print the classification name to the user.

Explanation of errors:

• The condition for Unhealthy for Sensitive Groups uses elif aqi >= 101 or aqi <= 150. The incorrect use of the logical OR (or) causes this condition to always evaluate as True for any input value. This is because any number will either be >= 101 or <= 150 (since these two ranges cover all possible numbers). For example:
  • For an input like 20, 20 <= 150 returns True, so this block runs.
  • For an input like 200, 200 >= 101 returns True, so this block runs.

This means all inputs will incorrectly map to "Unhealthy for Sensitive Groups" unless earlier conditions are satisfied.

• A similar issue exists for the Very Unhealthy condition (elif aqi >= 201 or aqi <= 300).

Corrected code:

To fix the issue, the logical ORs (or) in conditions like elif aqi >= 101 or aqi <= 150 should be changed to logical ANDs (and). Here’s the corrected code:

# Get the AQI.
aqi = int(input('Enter the Air Quality Index (AQI): '))

# Determine the classification of the AQI
# and display the result.
if aqi >= 0 and aqi <= 50:
    print('Good')
elif aqi >= 51 and aqi <= 100:
    print('Moderate')
elif aqi >= 101 and aqi <= 150:
    print('Unhealthy for Sensitive Groups')
elif aqi >= 151 and aqi <= 200:
    print('Unhealthy')
elif aqi >= 201 and aqi <= 300:
    print('Very Unhealthy')
else:
    print('Hazardous')

How the corrected code works:

• It uses and to ensure AQI falls within the specific range for a given category (e.g., aqi >= 101 and aqi <= 150 for "Unhealthy for Sensitive Groups").
• The ranges are checked in increasing order, so each category is exclusive and non-overlapping.

Sample input/output:

1. Input: 45

   • Output: Good

2. Input: 85

   • Output: Moderate

3. Input: 120

   • Output: Unhealthy for Sensitive Groups

4. Input: 155

   • Output: Unhealthy

5. Input: 220

   • Output: Very Unhealthy

6. Input: 350

   • Output: Hazardous