Simple precision control #64

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1. timlnx

   added

   enhancement

   on Mar 16, 2018
2. timlnx

   self-assigned this

   on Mar 16, 2018
3. kapsh commented on Mar 16, 2018

   

   kapsh

   on Mar 16, 2018

   Contributor

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   @tbielawa thanks for feedback.
   I already took a look into the code and found that best_prefix actually returns instance of suitable subclass of Bitmath. In this case it would be awkward to pass precision argument to the constructor.

   Next suggestion then. With custom __format__ magic method bitmath objects could partially understand format mini-language (like datetime objects). So I assume the usage example as:

   >>> size = bitmath.Byte(314159265)
   >>> size.best_prefix()
   MiB(299.60562229156494)
   >>> 'Size is {0:.2}'.format(size.best_prefix())
   Size is 299.61 MiB
   

   It looks quite pythonic IMO.
4. timlnx commented on Mar 17, 2018

   

   timlnx

   on Mar 17, 2018

   Last edited by timlnx

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   I see what you're going for. I didn't realize before that there is a magic __format__ method. I'm going to look at that closer.

   In the mean time, consider the following work-around as well: adjusting the default format string. As noted in the docs, each instance can already be formatted directory using the format method:

   In [15]: ex = bitmath.MiB(10.0/3.0)
   
   In [16]: print(ex)
   3.33333333333 MiB
   
   In [17]: print(ex.format('{value:0.2f} {unit}'))
   3.33 MiB

   However, if you want 2-digit precision by default, you can simply change the default formatting string:

   In [1]: import bitmath
   
   In [2]: bitmath.format_string = '{value:0.2f} {unit}'
   
   In [3]: ex = bitmath.MiB(10.0/3.0)
   
   In [4]: print(ex)
   3.33 MiB
   
   In [5]: print(ex.format('{value:0.2f} {unit}'))
   3.33 MiB

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