Dividing two very large numbers in python returns 1

Question

I know this question has been asked before but the solutions does not seem to be working for me. I have two very large numbers in python (2.7) like the followings:

a = 332413405639482828453084501713288536462658058395850
b = 332413405639482828453084501713288536462658058395856

and I need the result of

a/b

As you can see the there is a very tiny difference between the two so I assume the result of this division is not 0 or 1. I have tried // as suggested in other posts but that still does not return what I am looking for. Is there a solution to this or is it something impossible to do in python or with large numbers in general?

UPDATE: Btw, sorry but I forgot to mention that even by importing division from future I still do not get what I want.

Thanks

It's not simply an issue of integer to floating point conversion. Not a direct duplicate. — svens, Dec 16 '16 at 23:32

score 9 · Accepted Answer · answered Dec 16 '16 at 23:32

simple floats are not precise enough, try with the Decimal module

>>> from decimal import Decimal, localcontext
>>> with localcontext() as cont:
        cont.prec=100
        Decimal(a)/Decimal(b)


Decimal('0.9999999999999999999999999999999999999999999999999819501864298840350161830097171743383579489213731828')
>>>

score 2 · Answer 2 · edited May 23 '17 at 10:30

2

Since you're in Python 2 land (and not Python 3) you're experiencing integer division. Try float(a)/float(b)

edited May 23 '17 at 10:30

Community

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answered Dec 16 '16 at 23:25

Matt Messersmith

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You do not need to type-cast both numerator and denomenator. Type-casting any one of these will do the trick – Moinuddin Quadri Dec 16 '16 at 23:35
This is not the sole issue here. Try the same in Python 3. – L3viathan Dec 16 '16 at 23:51

Fejs · Answer 3 · 2016-12-16T23:35:27.480

1

I believe that it is impossible to achieve what You want. Precision with this big number can't be accomplished, so result would be presented as 1 in this particular case.

We can see exact value stored in float using decimal.Decimal (according to docs):

In [1]: a = 332413405639482828453084501713288536462658058395850

In [2]: b = 332413405639482828453084501713288536462658058395856

In [3]: import decimal

In [4]: a1 = decimal.Decimal(a)

In [5]: b1 = decimal.Decimal(b)

In [6]: a1/b1
Out[6]: Decimal('1.000000000000000000000000000')

edited Dec 16 '16 at 23:35

answered Dec 16 '16 at 23:31

Fejs

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So no matter what, I will always get 1 as an answer? – ahajib Dec 16 '16 at 23:31
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No, check my comment on your main question. Use the `decimal` module. – svens Dec 16 '16 at 23:33
1

@svens Great answer, I missed `prec` attribute. – Fejs Dec 16 '16 at 23:37

score 0 · Answer 4 · answered Dec 16 '16 at 23:25

0

Cast them into float first then do the division, otherwise u will get zero when the first integer is smaller than the second

answered Dec 16 '16 at 23:25

Steve Deng Zishi

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Dividing two very large numbers in python returns 1

4 Answers4