How to calculate decimals with 8 places?

Question

I have this number:

value='0.00000036'

as string I want to calculate how much is value*2 or value+value (0.00000072) and apparently it is not an easy task. I tried to use :

decimal.Decimal(value)

and it gets me with :

Decimal('3.6E-7')

Everything works fine when i'm using higher number (0.0000036) but it's useless to me.

Does this answer your question? [Convert float to string in positional format (without scientific notation and false precision)](https://stackoverflow.com/questions/38847690/convert-float-to-string-in-positional-format-without-scientific-notation-and-fa) — fdermishin, Dec 06 '20 at 19:56
@fdermishin It doesn't. I already have a string, I want to convert it to number, multiply, add and subtract and then display it. — user2396640, Dec 07 '20 at 07:50
So what is the problem? 3.6E-7 is the same as 0.00000036. Everything works as expected — fdermishin, Dec 07 '20 at 08:29

fdermishin · Accepted Answer · 2020-12-07T12:26:58.533

2

value='0.00000036'
decimal_value = decimal.Decimal(value)
print(format(decimal_value, 'f'))

0.00000036

If you want to multiply it by 2, just do it like so:

value='0.00000036'
decimal_value = decimal.Decimal(value) * 2
print(format(decimal_value, 'f'))

0.00000072

edited Dec 07 '20 at 12:26

answered Dec 06 '20 at 19:59

fdermishin

3,519
3
24
45

It doesn't answer the question of how to display the calculated of value+value. or value * 2. the excepted result should be 0.00000072 – user2396640 Dec 07 '20 at 07:44
Did you try multiplying it by 2 then? Like `format(decimal_value * 2, 'f')` – fdermishin Dec 07 '20 at 08:22
format(decimal_value * 2, 'f') gives me : ValueError: Unknown format code 'f' for object of type 'str' – user2396640 Dec 07 '20 at 08:24
You need to multiply by 2 variable of type Decimal, but not of type str – fdermishin Dec 07 '20 at 08:25

Sachin Rajput · Answer 2 · 2020-12-06T20:11:23.863

0

Just do this it will solve you problem of suppressing scientific notation.

import numpy as np
import decimal
value='0.00000036'
np.format_float_positional(decimal.Decimal(value), trim='-')

Output:'0.00000036'

edited Dec 06 '20 at 20:11

answered Dec 06 '20 at 20:04

Sachin Rajput

238
7
26

score 0 · Answer 3 · edited Dec 07 '20 at 09:01

0

Try to use f strings.

import decimal
value='0.00000036'
decimal_value = decimal.Decimal(value) * 2 # change * to + - / etc..
print(f'{decimal_value:f}') # means convert to float

Output:

0.00000072

edited Dec 07 '20 at 09:01

Tomerikoo

18,379
16
47
61

answered Dec 07 '20 at 08:49

ppwater

2,315
4
15
29

How to calculate decimals with 8 places?

3 Answers3