get decimal part of a float number in python

Question

I would like my Python2 daemon to wake up and do something exactly on the second.

Is there a better way to get the decmal part of a floating point number for a sleep time other then:

now = time.time()               #get the current time in a floating point format
left_part = long(now)           #isolate out the integer part
right_part = now - left_part    #now get the decimal part
time.sleep(1 - right_part)      #and sleep for the remaining portion of this second.

The sleep time will be variable depending on how much work was done in this second.

Is there a "Sleep till" function I don't know about? or, is there a better way to handle this?

I would like my daemon to be as efficient as possible so as not to monopolize too much CPU from other processes.

Thanks. Mark.

Did you try Googling your question's title (with spelling errors corrected)? — TigerhawkT3, May 07 '15 at 00:50
[Related question](https://stackoverflow.com/questions/3886402/python-how-to-get-numbers-after-decimal-point) — ChaimG, Dec 08 '17 at 02:36

Devin Jeanpierre · Answer 1 · 2015-05-07T02:18:57.423

17

time.sleep isn't guaranteed to wake up exactly when you tell it to, it can be somewhat inaccurate.

For getting the part after the decimal place, use the modulus (%) operator:

>>> 3.5 % 1
.5

e.g.:

>>> t = time.time()
>>> t
1430963764.102048
>>> 1 - t % 1
0.8979520797729492

As for "sleep til", you might be interested in the sched module, which is built around that idea: https://docs.python.org/2/library/sched

edited May 07 '15 at 02:18

answered May 07 '15 at 01:56

Devin Jeanpierre

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Thanks Devin. I think this is perfect. I guess when I said "exactly" I really meant "as close as possible". My real code line is now time.sleep(1 - time.time() %1). I love it. – Cool Javelin May 07 '15 at 23:54
Note, this goes funny if the number is negative. `-3.7 % 1` is 0.3, not 0.7. – Schwern Dec 21 '22 at 00:10

score 13 · Answer 2 · answered May 07 '15 at 00:48

13

Use math.modf()

math.modf(x) Return the fractional and integer parts of x. Both results carry the sign of x and are floats.

Example:

>>> from math import modf
>>> modf(3.1234)
(0.12340000000000018, 3.0)

answered May 07 '15 at 00:48

James Mills

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That’s some serious roundoff error, caused by internal binary conversion. That little discrepancy could be a problem in some cases, especially if you’ looking to comparing with other values. – Manngo Apr 15 '22 at 04:05

score 0 · Answer 3 · edited Feb 11 '20 at 05:33

0

n=(float(input('Enter the Decimal Value: ')))
n1=(str(n))
l=0
s=''
for c in n1:
    if c=='.' or l==1:
        l=1
        if c!='.':
            s+=c#storing the decimal part
# Converting the decimal part to the integer part
print('0.{0}'.format(int(s)))

in this process you'll get the absolute number of digits and acurate value of the floating values in python.

edited Feb 11 '20 at 05:33

Jim

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answered Jan 14 '19 at 09:26

Tuhin Mitra

555
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get decimal part of a float number in python

3 Answers3