mypy-nonfloat-decimal

Mypy non-float Decimal plugin

Restricts passing float numbers to Decimal

Why?

The implementation of floating point numbers can cause imprecisions in results. To avoid this problem you can use Decimal type, however you still need to avoid passing float as its parameter:

>>> Decimal(1.02)
Decimal("1.020000000000000017763568394002504646778106689453125")
>>> Decimal("1.02")
Decimal("1.02")

This plugin is meant to spot occurrences where float is passed to Decimal in your code.

Usage

• install plugin

pip install mypy-nonfloat-decimal

• add it into list of mypy plugins in your mypy config (mypy.ini)

[mypy]
plugins=mypy_nonfloat_decimal

• upon running mypy will detect float passed to Decimal and report it as an error (example.py):

from decimal import Decimal
Decimal(1.02)

$ mypy --config-file ./mypy.ini ./example.py

example.py:2: error: Invalid type passed to Decimal (expected "Union[int, str, Decimal]"), got float instead