Booleans, Comparisons, and Logic

A boolean is a value that is either True or False. Booleans are the answers to yes/no questions, and they are what drives every decision your programs make. In this lesson you will produce booleans by comparing values and combine them with logic.

What You'll Learn

• The True and False values
• Comparison operators that produce booleans
• Combining conditions with and, or, not
• Truthy and falsy values

True and False

Note the capital letters: True and False, not true or false.

Comparison Operators

Comparisons ask a question and answer with a boolean:

Watch out: = assigns a value, but == compares two values. Mixing them up is the most common beginner bug.

Chained Comparisons

Python lets you write a range check the way you would in math:

Combining Conditions: and, or, not

• and is True only if both sides are true
• or is True if at least one side is true
• not flips a boolean

Truthy and Falsy

In a yes/no context, some values act like False even though they are not literally False. Empty things (0, '', [], None) are falsy; almost everything else is truthy:

This is why you can write if my_list: to mean "if the list has anything in it," which you will use often.

Key Takeaways

• Booleans are True or False (capitalized)
• ==, !=, <, >, <=, >= compare values and return booleans
• = assigns, == compares
• and, or, not combine conditions
• Empty values are falsy; non-empty values are truthy