Quiz
Warm-up from lesson 3-2: after count = 4 and then count = count + 1, what is stored in count?
A third type: True or False
Every interesting feature of software is a decision: is this password correct, is the cart total over the free-shipping threshold, is this email spam? Before a program can decide anything, it needs a type whose whole job is to hold the answer to a yes/no question — that is what this lesson adds.
Strings hold text, ints and floats hold numbers. The third essential type is the boolean (named after the logician George Boole). A boolean has exactly two possible values: True or False. Note the capital first letter and no quotes, these are not strings.
Booleans usually come from comparisons:
| Operator | Question it asks | Example | Result |
|---|---|---|---|
== | equal? | 5 == 5 | True |
!= | not equal? | 7 != 7 | False |
< | less than? | 10 < 2 | False |
> | greater than? | 5 > 3 | True |
<= | less than or equal? | 3 <= 3 | True |
>= | greater or equal? | 2 >= 9 | False |
The big trap: = stores a value into a variable (lesson 3-1), while == asks whether two values are equal. Mixing them up is one of the most common beginner errors, so read them aloud differently: "gets" for =, "equals" for ==.
Code exercise · python
Predict each line's output (True or False), then run to check yourself.
Quiz
What is the difference between = and == in Python?
Code exercise · python
Your turn. Write two print lines that output True then False, using comparisons (not by printing the words directly): first compare 100 >= 100, then compare the strings "cat" and "dog" for equality.