Any way to control precision with best_prefix() methods????

now I can convert the unit automaticly .

b_size = Byte(bucket.head_object(obj_name).content_length)
 return b_size.best_prefix().__str__()  //379.051757812 KiB

but the return is too long
any way I can control the precision of the return value??
For example:
379.051757812 KiB To 379.05 KiB

[timlnx]

Sorry it took me so long to get back to you. Thanks for waiting 😄

Yes @tyan4g, complete control over result format is possible. Setting decimal precision is done through use of the format method. Here's an example for you:

>>> import bitmath
>>> b_size = bitmath.KiB(379.051757812)

>>> # This is what you are seeing now:
>>> b_size.best_prefix()
KiB(379.051757812)

>>> # this truncates the decimal precision to just 3 digits and returns a string:
>>> b_size.best_prefix().format('{value:.3f} {unit}')
'379.052 KiB'

This method is similar to the native Python format method, and you feed it parameters in much the same way. The words you see in there, {value} and {unit} are instance attributes of the object you are trying to format. The complete list of instance attributes is also documented for your perusal:

• Bitmath Instance Attributes

Bitmath also includes a context manager to selectively change how bitmath instances are formatted. Using the bitmath.format context manager all printing and what have you inside of the context manager follows the specification you provide.

bitmath.format([fmt_str=None[, plural=False]])

With this you can set the formatting string yourself, like the earlier example I showed with the {value} and {unit} attributes. You can also say that anything printed should use plural units (MiBs, kBs, etc).

#!/usr/bin/env python
import bitmath

def print_sizes(s1, s2):
    print """{}
{}
""".format(size1, size2)

size1 = bitmath.KiB(379.051757812)
size2 = bitmath.GiB(1)/3

print "Default precision:"
print_sizes(size1, size2)

print "3 digit precision:"
with bitmath.format('{value:.3f} {unit}'):
    print_sizes(size1, size2)

print "Plural units:"
with bitmath.format('{value:.3f} {unit}', plural=True):
    print_sizes(size1, size2)

And if you were to run this you would see results like such:

379.051757812 KiB
0.333333333023 GiB

3 digit precision:
379.052 KiB
0.333 GiB

Plural units:
379.052 KiBs
0.333 GiBs

I hope that helps 👍 Please respond to this issue again if you have any more trouble. Thanks for using bitmath!

[kapsh]

@tbielawa thanks for explanation here, now I can find it in the documentation too: http://bitmath.readthedocs.io/en/latest/instances.html?highlight=precision#setting-decimal-precision
But this is very verbose and slightly inconvenient for frequent use. What do you think about adding precision argument to best_prefix method as shortcut for most commonly required operation?

[timlnx]

I like your idea and want to find a way to implement what you're looking for. It can't be done the way you suggested but that doesn't mean it's impossible.

I made a new issue just now to track this (#64). Thanks for coming back, I love community engagement!