Python large numbers

[kroq-gar78]

Hello Ubuntu Forums community,

I am making a python program that requires the math.pow function. I need it to go up to 2^31 (2 to the 31st power) and preferably even farther. When I run the program in the terminal, it says "OverflowError: math range error"

Any way to fix this?
Thanks in advance.

[Bachstelze]

What are you doing, exactly? math.pow(2, 32) doesn't raise an exception for me.

[Queue29]

Python supports arbitrary precision numbers out of the box. What version are you using? And can you post the code that seems to be troublesome?

[ssam]

Python supports arbitrary precision numbers out of the box. What version are you using? And can you post the code that seems to be troublesome?

thats not right. its just long ints that have infinite range.

http://docs.python.org/library/stdty...t-long-complex

>>> math.sin(pow(2,1000))
-0.15920170308624243
>>> math.sin(pow(2,10000))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OverflowError: long int too large to convert to float

[worksofcraft]

thats not right. its just long ints that have infinite range.

http://docs.python.org/library/stdty...t-long-complex

>>> math.sin(pow(2,1000))
-0.15920170308624243
>>> math.sin(pow(2,10000))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OverflowError: long int too large to convert to float

I thought it would calculate pow as floating point number anyway... what on Earth is Python doing... 10000 multiplications?

Anyway as far as I can tell most languages use floating point as provided by their processor which is usually IEEE-754. I think it give about 16 digits of precision and exponent up to something like 300 in decimal.

[Bachstelze]

I thought it would calculate pow as floating point number anyway... what on Earth is Python doing... 10000 multiplications?

pow is integer, math.pow is float.

>>> pow(2, 1000)
10715086071862673209484250490600018105614048117055336074437503883703510511249361224931983788156958581275946729175531468251871452856923140435984577574698574803934567774824230985421074605062371141877954182153046474983581941267398767559165543946077062914571196477686542167660429831652624386837205668069376L
>>> math.pow(2, 1000)
1.0715086071862673e+301

Incredible as it may sound, having integer powers is actually very useful. When doing arithmetic for example.

[kroq-gar78]

Thanks Bachstelze. I didn't know there was just pow() and that there was a difference between pow() and math.pow().

Marking thread as solved.

[Bachstelze]

Thanks Bachstelze. I didn't know there was just pow() and that there was a difference between pow() and math.pow().

Marking thread as solved.

Yup, this is why you should never do

from math import *

[CptPicard]

pow is integer, math.pow is float.

Well, unless you give pow float parameters.

That math.pow is specifically a float is interesting; could be one of these rare cases where I might actually agree with worksofcraft's objections to Python's handling of number types.

[Bachstelze]

Well, unless you give pow float parameters.

That math.pow is specifically a float is interesting; could be one of these rare cases where I might actually agree with worksofcraft's objections to Python's handling of number types.

It makes sense to me. As I said, in some applications you really want full-precision exponentiation of integers (e.g. when doing RSA crypto), but on the other hand, sometimes you don't need the precision, and having long integers is just a bother.

Having both is a nice thing about Python IMO.