Added __format__ method

[jonathaneunice]

• allows specifying precision in inline string formatting
• e.g. 'size: {:0.1f}'.format(s)
• using standard string formatting, not just bitmath.format
• adds corresponding tests

Short description: Adds a format method to enable in-line string interpolation

If you have a bitmath object (of whatever unit), it's handy to be able to interpolate that value directly in a format string. E.g.:

size = bitmath.MiB(2.847598437)
print('size: {:.1f}'.format(size))

A__format__ method makes this possible. It's even neater in Python 3.6 and following, with its ability to automatically interpolate variables into strings.

size = bitmath.MiB(2.847598437)
print(f'size: {size:.1f}')

[jonathaneunice]

The CI failures appear to be related to outdated configuration of the requirements, which I did not change, not test breakage.

[jonathaneunice]

Using modern python3 versions (the 3.3 branch ended its official supported life on September 29, 2017), the tests pass.

[tbielawa]

Thanks for the PR! I'll try to take a gander at this today. I'm excited about this one.

[tbielawa]

I'd like this squashed down into a shorter number of commits if you can please. One or a couple, whichever makes more sense to you.

[tbielawa]

@jonathaneunice this is a nice PR, do you still feel like trying to get this cleaned up and able to merge?

[florisla]

It would be great to include this in bitmath. Especially with Python 3.6's f-strings.

byte_counts = [1, 1025, 1026*1024, 1027*1024*1024, 1028*1024*1024*1024]
for byte_count in byte_counts:
    size = bitmath.Byte(byte_count).best_prefix()
    print(f"{size.value:8.3f} {size.unit:>4}"))

1.000 Byte
1.001  KiB
1.002  MiB
1.003  GiB
1.004  TiB