Booleans and Comparisons

Python for Absolute Beginners · Lesson 8

What you’ll learn

• What a boolean is: True and False
• How comparisons ask yes-or-no questions
• All six comparison operators
• How to store a comparison's answer in a variable
• Why = and == are different, and why mixing them up is the classic beginner bug

True or False: the boolean

• A boolean is a value that can only be one of two things: True or False — no maybe, no in-between
• Named after the mathematician George Boole
• Note the capital letters: Python writes True and False with a capital first letter
• Lowercase true gives a NameError — Python only recognizes the capitalized forms

Booleans in code

print(True)
print(False)

Output:
True
False

On their own, True and False are not very interesting — they become powerful when a comparison produces one.

Comparisons ask yes-or-no questions

• A comparison compares two values and answers True or False
• == equal to · != not equal to · > greater than · < less than
• >= greater than or equal to · <= less than or equal to
• Comparisons work on strings too, in dictionary (alphabetical) order

Comparisons in code

print(10 > 9)
print(10 < 9)
print(10 == 10)
print(10 != 9)
print(7 >= 7)
print(7 <= 6)

Output:
True
False
True
True
True
False

Each line asks a yes-or-no question, and Python answers True or False.

Comparing strings in code

print("apple" < "banana")
print("Sam" == "Sam")

Output:
True
True

“apple” comes before “banana” alphabetically, so the first answer is True.

Storing the answer

• A comparison's answer is just a value, so it can live in a variable like anything else
• Storing the answer separately keeps the decision readable — the variable's name says what the question meant
• In Lesson 9, you will use variables like this to make decisions

Storing the answer in code

age = 12
old_enough = age >= 10
print(old_enough)

Output:
True

old_enough now holds True — the answer to “is age 10 or older?”

The classic bug: = versus ==

• = stores a value: age = 12 puts 12 into age
• == asks whether two values are equal: age == 12 answers True or False
• Using one = where you meant two does not ask a question — it stores a value, usually by accident
• If a comparison ever seems to “always be true,” check whether you wrote = instead of == first

Hands-on exercise

• In the shell, work out each of these before running them, then check: 5 > 3, 5 < 3, 5 == 5, 5 != 5, 4 >= 4, 4 <= 3
• Store your age in a variable, then store the answer to “am I 10 or older?” in a second variable and print it
• Compare two names with == — once with the same name twice, once with different names — and explain both results

Key takeaways

• A boolean is True or False, always capitalized
• Comparisons (==, !=, >, <, >=, <=) answer yes-or-no questions
• A comparison's answer can be stored in a variable for later use
• = stores; == asks. Mixing them up is the classic beginner bug

Take the quiz

Take the Lesson 8 quiz — 5 quick questions to check what you learned.

Next lesson

If Statements: Making Decisions