Python Comparison Chaining: Writing Range Checks

This guide explains Comparison Chaining: Writing Range Checks through a focused example and practical reasoning. No prior knowledge of this specific operation is required.

Understanding the Concept

Python supports chained comparisons, so lower <= value < upper expresses an interval directly. Each middle expression is evaluated once, and the chain stops when a link fails.

When You Would Use This

Accept a temperature inside an allowed operating range.

Step-by-Step Example

temperature_c = 24
within_range = 18 <= temperature_c <= 28
print(within_range)
print(0 <= -1 < 100)
print(3 < 5 < 9)

How the Example Works

The first and third checks return True; the middle check returns False. The chain behaves like adjacent and comparisons but avoids repeating temperature_c.

Example Output

True
False
True

Try It Yourself

Write a range check that accepts ages 13 through 19 inclusive.

Common Beginner Mistakes

Using 18 <= x >= 28 when an upper bound was intended.
Confusing strict < with inclusive <= at the boundaries.
Assuming chained equality expressions enforce the same conditions as chained ordering.

Key Takeaways

Python supports chained comparisons, so lower <= value < upper expresses an interval directly.
The first and third checks return True; the middle check returns False.
Avoid this mistake: Using 18 <= x >= 28 when an upper bound was intended.