get number that is raised to the power of

[Astan Chee]

Hi,
Im not sure if this is more of a math question or a python question. I
have a variable in python:is there a way to find the value of n if i know only v aside from
str(v).split('+')[1] ? that seems like too much of a hack and I was
wondering if there was a faster way of doing it?
Thanks for any pointers
Astan

--
"Formulations of number theory: Complete, Consistent, Non-trivial. Choose two."


Animal Logic
http://www.animallogic.com

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[Marc 'BlackJack' Rintsch]

Hi,
Im not sure if this is more of a math question or a python question. I
have a variable in python:is there a way to find the value of n if i know only v aside from
str(v).split('+')[1] ? that seems like too much of a hack and I was
wondering if there was a faster way of doing it?

That hack isn't even working properly because ``str(10.0**1)`` has no '+'
in its string representation.

Solution:

n = math.log(v, 10)

Ciao,
Marc 'BlackJack' Rintsch

 

[Boris Borcic]

Hi,
Im not sure if this is more of a math question or a python question. I
have a variable in python:

v = 10.0**n

is there a way to find the value of n if i know only v aside from
str(v).split('+')[1] ?

Astan, you could try something like (n for n in range(1,100) if
10.0**n==v).next() or like len(str(int(v)))-1

Faster ?! How fast do you need it to be ?

That hack isn't even working properly because ``str(10.0**1)`` has no '+'
in its string representation.

OTOH "%.0e" % (10.0**1) does
....but "%.0e" % (10.0**-1) of course doesn't

Solution:

n = math.log(v, 10)

Ciao,
Marc 'BlackJack' Rintsch

Beware of floating point approximations, though. Eg

Traceback (most recent call last):
File "<pyshell#12>", line 1, in <module>
assert log(10**3,10)==3
AssertionError

Cheers, BB