decimal when exact decimal precision matters

decimal gives you exact decimal arithmetic, which is often a better fit than float when precision and rounding rules matter.

Why it is useful

Floating-point arithmetic can surprise people:

print(0.1 + 0.2)

With Decimal, you get exact decimal semantics:

from decimal import Decimal

total = Decimal("0.1") + Decimal("0.2")
print(total)

Output:

0.3

Good use cases

• money values
• invoices and totals
• explicit rounding rules
• domains where decimal precision matters

One important detail

Create Decimal values from strings when precision matters. Starting from a float can carry float imprecision into the result.

Rules of thumb

• Use decimal when exact decimal behavior matters.
• Create Decimal values from strings.
• Prefer float only when approximate numeric work is acceptable.