How to return a big number in a plain format?

Question

I want to return a big number in a plain format but instead I'm getting this:

>>> x=1000000000000000000000000000000
>>> int(1*x/100) # try to get 1% of x
9999999999999999583119736832 # <------------ here

I was expecting 10000000000000000000000000000, how do I achieve this?

https://stackoverflow.com/questions/588004/is-floating-point-math-broken — hiro protagonist, Jun 23 '22 at 04:49

score 2 · Answer 1 · answered Jun 23 '22 at 04:55

2

Floating point arithmetic has Issues and Limitations.

In your case simply avoid it by using integer division:

>>> x=1000000000000000000000000000000
>>> x=x//100
>>> x
10000000000000000000000000000

answered Jun 23 '22 at 04:55

gimix

3,431
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Lazyer · Accepted Answer · 2022-06-23T05:04:57.273

0

You can use decimal to handle the decimal point more precisely.

It provides fast correctly-rounded decimal floating point arithmetic. In contrast, numbers like 1.1 and 2.2 do not have exact representations in binary floating point. Decimal numbers can be represented exactly and in decimal floating point.

from decimal import Decimal
x = Decimal(1000000000000000000000000000000)
print(int(1*x/100))  # 10000000000000000000000000000

edited Jun 23 '22 at 05:04

answered Jun 23 '22 at 04:44

Lazyer

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1
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What do you get with this when you divide by 3 instead? – Kelly Bundy Jun 23 '22 at 04:51
the decimal module has a user alterable precision (defaulting to 28 places) which can be as large as needed for a given problem. – Lazyer Jun 23 '22 at 04:52
1

@hiroprotagonist As it converts to int, they'd be better off simply using floor division. That gives better results (and is faster and less code). – Kelly Bundy Jun 23 '22 at 04:53
@KellyBundy whats floor division? – dape11 Jun 23 '22 at 04:54
Is using Decimal same as doing `int(1*x//100)` ? i am getting same result as @Lazyer – dape11 Jun 23 '22 at 04:55
@dape11 https://docs.python.org/3/reference/expressions.html#binary-arithmetic-operations – Kelly Bundy Jun 23 '22 at 04:56
@dape11 **int(1*x//100)** is little different with **"/"** operation. **decimal** doesn't work with **"//"** operation. – Lazyer Jun 23 '22 at 04:58

How to return a big number in a plain format?

2 Answers2