An employee roster must select active records and print them in order.
What You Need to Understand
This checkpoint combines indexing, iteration, filtering, and mutation. The central skill is choosing the correct sequence operation and verifying what changes the original object.
When to Use It
An employee roster must select active records and print them in order.
Step-by-Step Python Example
records = [("Maya", True), ("Avi", False), ("Noa", True)]
active_names = [name for name, active in records if active]
for number, name in enumerate(active_names, start=1):
print(number, name)How the Example Works
The comprehension selects two active names. enumerate() supplies numbering for display, without changing the source tuples.
Example Output
1 Maya
2 Noa
[70, 90]A Second Example
Compare this smaller variation with the main example, then experiment with your own values.
grades = [70, 90, 60]
print([grade for grade in grades if grade >= 70])Important Behavior and Edge Cases
Do not confuse tuples with deeply frozen records or assume a comprehension mutates its input.
Try It Yourself
Rewrite the comprehension with explicit loops and compare the resulting lists.
Common Beginner Mistakes
- Do not confuse tuples with deeply frozen records or assume a comprehension mutates its input.
- Overlooking how an iterable is consumed, how element positions are chosen, or whether a function creates a new list.
Key Takeaways
- This checkpoint combines indexing, iteration, filtering, and mutation.
- The comprehension selects two active names.
- Do not confuse tuples with deeply frozen records or assume a comprehension mutates its input.