Different division result python

Question

I have some strange result in my python 3.6.3. Once i tried some code and i reach this problem.

>>> a = 10**32
>>> print(a/1000/1000)
9.999999999999999e+25

As you see it not actually right, but if i go other way, i reach what i expect

>>> print(a/1000000)
1e+26

Same thing with

>>> 10**26
>>> 10**31

Can somebody explain me what's wrong? i tried write it in one line no result

try integer division `a//1000//1000`, you'll get `100000000000000000000000000` — Jean-François Fabre, Apr 12 '18 at 16:47
integer division works cleary right, but why double division by 1000 and division by 10**6 have different results — B31aim, Apr 12 '18 at 16:48

score 1 · Answer 1 · answered Apr 12 '18 at 16:49

1

>>> a = 10**32
>>> a/1000/1000
9.999999999999999e+25

As you know, Python 3 division is no longer an integer division (a//1000//1000 would have worked fine), so you're performing 2 floating point divisions here, introducing an (unnecessary) floating point accumulation error.

>>> a/1000000
1e+26

this only performs one division, so lower floating point error effect, even if result is now floating point.

answered Apr 12 '18 at 16:49

Jean-François Fabre

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Thanks. Now i understand this principe of floating point operation. – B31aim Apr 12 '18 at 16:56

Different division result python

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