Booleans, None, and Comparisons

🎯 Learning Objective

After this lesson, you will be able to:

• Use Python's True, False, and None values correctly.
• Compare values with equality, ordering, and chained comparisons.
• Check optional values with is None and is not None.
• Combine boolean expressions with and, or, and not.

Short Explanation

Python boolean values are True and False with capital letters. Comparisons such as ==, !=, <, <=, >, and >= produce boolean results that can be stored, printed, or later used in conditions.

Python also supports chained comparisons:

minimum <= value <= maximum

This reads naturally and evaluates whether the value satisfies both boundaries.

None represents the absence of a value. Use is None or is not None for this special value rather than treating it like an ordinary string or number.

Logical operators are words in Python: and, or, and not. Comparisons run before not, then and, then or. Parentheses are still useful when a business rule contains several parts.

💡 Tip: Use == to compare ordinary values. Reserve is for identity checks, especially None.

Clean Code Examples

1. Produce boolean results with comparisons

Each comparison evaluates to True or False.

status = "ready"
attempts = 2

print(status == "ready")
print(attempts < 3)

Output:

True
True

2. Check an optional value

Use identity checks when a value may be missing.

last_error = None

print(last_error is None)
print(last_error is not None)

Output:

True
False

3. Combine a policy with logical operators

Every required part of this policy must be true.

role = "editor"
account_active = True

can_publish = role == "editor" and account_active
print(can_publish)

Output:

True

4. Check an inclusive range

A chained comparison can express both boundaries clearly.

latency_ms = 180

print(100 <= latency_ms <= 250)
print(not latency_ms > 500)

Output:

True
True

⚠️ Common Mistakes

1. Do not write true, false, null, &&, ||, or ! in Python.
2. Do not use assignment = when you need equality comparison ==.
3. Do not write value == None as the preferred missing-value check.
4. Do not write status == "failed" or "queued"; each side of or must be a complete boolean expression.