Python float to Decimal conversion

Question

Python Decimal doesn\'t support being constructed from float; it expects that you have to convert float to a string first.

This is very inconvenient since standard

Answer 1

Python <2.7

"%.15g" % f

Or in Python 3.0:

format(f, ".15g")

Python 2.7+, 3.2+

Just pass the float to Decimal constructor directly, like this:

from decimal import Decimal
Decimal(f)

Answer 2

When you say "preserving value as the user has entered", why not just store the user-entered value as a string, and pass that to the Decimal constructor?

Answer 3

The "official" string representation of a float is given by the repr() built-in:

>>> repr(1.5)
'1.5'
>>> repr(12345.678901234567890123456789)
'12345.678901234567'

You can use repr() instead of a formatted string, the result won't contain any unnecessary garbage.