7.19 Hands-on Exercises & Mini Projects

CPU Usage Calculator

Build a function that takes total CPU time used and elapsed time, and returns the percentage utilization using arithmetic operators.

def cpu_utilization(used_seconds, elapsed_seconds):
    return (used_seconds / elapsed_seconds) * 100

>>> cpu_utilization(45, 60)
75.0

Disk Usage Alert

Build a function that returns an alert message using comparison operators against a configurable threshold.

def check_disk(percent_used, threshold=90):
    return "ALERT" if percent_used > threshold else "OK"

>>> check_disk(95)
'ALERT'

Status Code Validator

Build a function using chained comparisons to classify any HTTP status code into its category.

def classify_status(code):
    if 200 <= code < 300:
        return "Success"
    elif 300 <= code < 400:
        return "Redirect"
    elif 400 <= code < 500:
        return "Client Error"
    else:
        return "Server Error"

>>> classify_status(301)
'Redirect'

Service Health Checker

Build a function combining logical operators to determine overall service health from multiple boolean signals.

def is_healthy(is_running, response_time_ms, error_rate):
    return is_running and response_time_ms < 500 and error_rate < 0.05

>>> is_healthy(True, 230, 0.01)
True
>>> is_healthy(True, 800, 0.01)
False

Quick Interview Answer

“These exercises reinforce the chapter’s core ideas hands-on: the CPU calculator exercises arithmetic (/ and *), the disk alert exercises comparison plus the ternary operator, the status validator exercises chained comparisons across an if/elif ladder, and the health checker exercises and-chained logical operators with short-circuit evaluation skipping later checks once an earlier one already fails.”

Common Mistakes

• Using / where // was intended (or vice versa) in the CPU calculator, producing a fractional result where a whole number was expected, or a truncated one where precision mattered.
• Writing the status validator as separate if statements instead of if/elif, letting multiple branches match and return inconsistent results.
• Ordering the health checker’s conditions without considering short-circuit performance — putting an expensive check before a cheap one that’s more likely to fail first.