Numeric Data Types

Updated Oct 28, 2019 ·

Overview

Python has several built-in ways to handle numbers.

• Integers are for whole numbers
• Floats are for approximate or fractional numbers
• Decimals are for precise values, like money

Integers and floats are enough for most calculations, but decimals are useful when exact precision is needed.

Decimals

Decimals let you avoid rounding errors and keep exact values. You need to import them from the decimal module.

In the example below, Decimal is used to store precise values:

from decimal import Decimal

price = Decimal("19.99")
tax = Decimal("0.07")
total = price + (price * tax)
print(total)

Output:

21.3893

Decimals help keep calculations accurate, especially for currency or precise measurements.

Floats

Floats can sometimes display in scientific notation. You can control how many decimal places appear using f-strings.

• Small numbers may show as 1e-05
• f-strings format the number neatly
• specify precision with .Xf where X is number of decimals

Example formatting a float:

value = 0.00001
print(f"{value:f}")
print(f"{value:.7f}")

Output:

0.000010
0.0000100

Python Division

Python supports two division types:

• Normal float division: / returns a float result
• Floored division: // returns the whole number part only

Example with numbers:

print(4 / 2)
print(7 // 3)

Output:

2.0
2

Floored division is useful when you need integer results without rounding.

Booleans

Booleans are used for true/false values and for checking conditions in code. They act like an "on/off" switch.

For example, setting a flag and checking it with an if statement:

is_hungry = True

if is_hungry:
    print("Time to eat!")

Output:

Time to eat!

Truthy and Falsey Values

Beyond True and False, other values can also behave like booleans. Python treats values as truthy or falsey in conditions.

Value type	Boolean behavior	Example
Numbers	0 is falsey, non-zero is truthy	0, 2, -5
Strings, lists, dictionaries	Empty is falsey, non-empty is truthy	"", "hi", [], [1], {}
None	Always falsey	None

For example, using numbers in a condition:

apples = 2

if apples:
    print("You have apples!")

apples = 0

if not apples:
    print("No apples left.")

Output:

You have apples!
No apples left.

You can also check if a value is "truthy" or "falsey" using the bool() function, which converts any value to its boolean equivalent.

In the example below, values contains different types, and bool() is used to evaluate them:

values = [0, 1, "", "hello", [], [5], None]

for v in values:
    print(f"{v}: {bool(v)}")

Output:

0: False
1: True
: False
hello: True
[]: False
[5]: True
None: False

Boolean Operators

Operators can be used to compare values and return booleans.

• == checks equality
• !=, <, <=, >, >= check other comparisons

Example comparing cookie quantities:

cookie_qty = 3

print(cookie_qty == 3)  
print(cookie_qty > 5)  

Output:

True
False

Floats and Boolean Checks

Float numbers may not be exact due to how Python stores them, so comparing float with == can give unexpected results. To keep the comparisons precise, you can use rounding or tolerances.

Example:

value = 0.1 + 1.1

print(value == 1.2)  # "might be" False
print(value)         # shows small difference

Output:

False
1.2000000000000002