On 3 aug 2008, at 17.16, Ed**********@Ve rizonWireless.c om wrote:
for nth square root: use math.sqrt n times for example
Ehum. The OP wants to compute the nth root ( not the nth square root)
>
>>>import math num = 625 how_many_sqr t = 2 for i in range(how_many_ sqrt):
.. num = math.sqrt(num)
..
>>>num
5.0
all comparisons work fine for arbitrary floating point numbers...
For readability print them with required precision. for example
>>>a = .2 b = .4 b = b/2 a == b
True
>>>a, b
(0.200000000000 00001, 0.2000000000000 0001)
>>>'%.2f' % a, '%.2f' % b
('0.20', '0.20')
>>>>
thx. Edwin
-----Original Message-----
From: py************* *************** *************** *******@python. org
[mailto:py****** *************** *************** **************@ python.org
]
On Behalf Of CNiall
Sent: Sunday, August 03, 2008 10:03 AM
To: py*********@pyt hon.org
Subject: Decimals not equalling themselves (e.g. 0.2 = 0.2000000001)
I am very new to Python (I started learning it just yesterday), but I
have encountered a problem.
I want to make a simple script that calculates the n-th root of a
given
number (e.g. 4th root of 625--obviously five, but it's just an example
:P), and because there is no nth-root function in Python I will do
this
with something like x**(1/n).
However, with some, but not all, decimals, they do not seem to 'equal
themselves'. This is probably a bad way of expressing what I mean, so
I'll give an example:
>>>0.5
0.5
>>>0.25
0.25
>>>0.125
0.125
>>>0.2
0.2000000000000 0001
>>>0.33
0.3300000000000 0002
As you can see, the last two decimals are very slightly inaccurate.
However, it appears that when n in 1/n is a power of two, the decimal
does not get 'thrown off'. How might I make Python recognise 0.2 as
0.2
and not 0.2000000000000 0001?
This discrepancy is very minor, but it makes the whole n-th root
calculator inaccurate. :\
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Tommy Nordgren to************@ comhem.se 0 1115 This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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I am very new to Python (I started learning it just yesterday), but I
have encountered a problem.
I want to make a simple script that calculates the n-th root of a given
number (e.g. 4th root of 625--obviously five, but it's just an example
:P), and because there is no nth-root function in Python I will do this
with something like x**(1/n).
However, with some, but not all, decimals, they do not seem to 'equal
themselves'. This is...
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for nth square root: use math.sqrt n times for example
... num = math.sqrt(num)
...
5.0
all comparisons work fine for arbitrary floating point numbers...
For readability print them with required precision. for example
True
(0.20000000000000001, 0.20000000000000001)
('0.20', '0.20')
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2008/8/3 CNiall <cniall@icedcerulean.com>:
The golden rule is that working with decimals (in pretty much any
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--
Tim Rowe
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