Question

Similar posts such as the following do not answer my question.
Convert a string to integer with decimal in Python

Consider the following Python code.

>>> import decimal
>>> s = '23.456'
>>> d = decimal.Decimal(s)
>>> d
Decimal('23.456')           # How do I represent this as simply 23.456?
>>> d - 1
22                          # How do I obtain the output to be 22.456?

How do I convert a string to a decimal number, so I am able to perform arithmetic functions on it and obtain an output with the correct precision?

Answer 1

If you want to stay in decimal numbers, safest is to convert everything:

>>> s = '23.456'
>>> d = decimal.Decimal(s)

>>> d - decimal.Decimal('1')
Decimal('22.456')
>>> d - decimal.Decimal('1.0')
Decimal('22.456')

In Python 2.7, there’s an implicit conversion for integers, but not floats.

>>> d - 1
Decimal('22.456')
>>> d - 1.0
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for -: 'Decimal' and 'float'