Data in Programs

Mad Libs and The Dice Roller look like cousins, but under the hood they handle opposite kinds of cargo — one stitches text together, the other does arithmetic on numbers. Programs care about that difference far more than people do.

Three kinds of data

Kind	Python name	Example	Built for
Numbers	int, float	17, 9.75	arithmetic and comparing
Text	str	"hello"	joining, printing, replacing
True/false	bool	True	decisions in Conditionals

17 and "17" look almost identical on screen. To Python they are as different as a number and a photograph of a number — only one of them can do math.

Why the type matters

input() always hands you text, no matter what the user typed. That one fact is the source of a whole family of beginner bugs:

guests = input("How many guests? ")   # user types 4
print(guests * 2)        # prints 44 — text gets repeated
print(int(guests) * 2)   # prints 8 — convert, then do math

The fix is one honest question: what kind of data is this, really? Half the mysteries in Spot the Bug dissolve the moment you ask it.

Expressions and order of operations

When writing expressions that combine numbers, text, or comparisons, Python evaluates operators in a strict order of operations:

1. Parentheses () — evaluate innermost brackets first.
2. Exponents ** — powers calculated next.
3. Multiplication *, Division /, Floor Division //, Modulo % — evaluated left to right.
4. Addition +, Subtraction - — evaluated left to right (+ also concatenates strings).
5. Comparisons (<, <=, >, >=, ==, !=) — produce boolean True or False.
6. Logical operators (not, and, or) — evaluate boolean logic.

Understanding precedence prevents subtle logic errors, such as calculating an average (a + b) / 2 versus a + b / 2. Operators Practice drills these evaluation rules.

Where data comes from

Programs rarely invent their data. It arrives from a person typing at input(), from chance — random.randint rolling for The Dice Roller — from files you saved earlier, or from another program entirely. Wherever it comes from, the first job is always the same: know its type, convert it if needed, and only then put it to work. Variables and Expressions Practice drills exactly that routine until it is reflex.

Curriculum connection

C1.3

identify various types of data and explain how they are used within programs

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C1.4

determine the appropriate expressions and instructions to use in a programming statement, taking into account the order of operations

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C2.2

write programs that use and generate data involving various sources and formats

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