Python formatting large values

Question

Below is the code for formatting an x value that I have been using.

Examples of what does it do:

• It formats 7,500,000 into 7.5 M

• It form

Answer 1

There's probably a shorter way to generate the format strings; but they're easy enough to just map to each magnitude. I don't fully understand the behavior you want w/r/t decimal point length, but the logic for that should be easy.

Since what you had was a method, I incorporated this into a class. (This also avoids defining formats every time the function is called.)

from math import log10

class Formatter(object):
    def __init__(self):
        self.formats = (('%1.1f', 0),
                        ('%2.1f', 0),
                        ('%1.2f K', 3),
                        ('%1.2f K', 3),
                        ('%2.1f K', 3),
                        ('%1.2f M', 6),
                        ('%1.2f M', 6),
                        ('%2.1f M', 6),
                        ('%1.2f B', 9),
                        ('%1.2f B', 9),
                        ('%2.1f B', 9),
                        ('%1.2f T', 12),
                        ('%1.2f T', 12),
                        ('%2.1f T', 12))

    def human_readable(self, x):
        if x == 0: return '0'
        magnitude = int(log10(abs(x)))
        if magnitude > 13: format_str, denominator_mag = '%i T', 12
        else: format_str, denominator_mag = self.formats[magnitude]
        return (format_str % (x * 1.0 / (10 ** denominator_mag))).lstrip('0')

Edit: Here's one that doesn't use a lookup table:

def human_readable(self, x):
    if x == 0: return '0'
    magnitude = int(log10(abs(x)))
    if magnitude > 13: 
        format_str = '%i T'
        denominator_mag = 12
    else: 
        float_fmt = '%2.1f ' if magnitude % 3 == 1 else '%1.2f '
        illion = (magnitude + 1) // 3
        format_str = float_fmt + ['', 'K', 'M', 'B', 'T'][illion]
        denominator_mag = illion * 3
    return (format_str % (x * 1.0 / (10 ** denominator_mag))).lstrip('0')

Answer 2

Try all the different possible ways to format it and pick the shortest one length-wise, with preference given to larger units (e.g., prefer .55 B to 550 M, since they are the same length).

As for stripping leading zeros, one possible solution is checking if s[:2] == '0.' and replacing it with '.'