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Short Number Formatting in Python

Yesterday I wrote a blog post about creating short number formats in JavaScript. Definitely check out that post first, but the idea was to take something like 9496301 and display it as 9.5M. In that post, I used the built-in Intl object and it worked really well. It got me thinking, could you do the same in Python?

First off, I checked and was happy to see that like JavaScript, Python supports numeric separators. This makes it much easier to read large numbers in code. It also meant I could take my test array and copy and paste it into a Python program:

inputs = [ 999, 1000, 2999, 12_499, 12_500, 430912, 9_123_456, 1_111_111_111, 81_343_902_530, 1_111_111_111_111, 62_123_456_789_011, 1_111_111_111_111_111,
]

I literally just now noticed that Python is also ok with the trailing comma. Sweet. Ok, so first I checked into just regular number formats, and of course, Python supports that, both with a built-in format function and f strings. In my case I wasn’t worried about decimal places and the like, but could easily add commas. Here’s a simple example:

for i in inputs: print(f"{i:<30}{i:,}")

The first time I print the value, I don’t format it, but pad it 30 characters to make my output easier to read. The formatting is done in the second variable, by just supplying :,. Here’s the output:

999 999
1000 1,000
2999 2,999
12499 12,499
12500 12,500
430912 430,912
9123456 9,123,456
1111111111 1,111,111,111
81343902530 81,343,902,530
1111111111111 1,111,111,111,111
62123456789011 62,123,456,789,011
1111111111111111 1,111,111,111,111,111

Commas work for some countries, but not all. I checked and there’s a locale-specific version as well: :n. Here’s an example where I set the locale to German.

999 999
1000 1.000
2999 2.999
12499 12.499
12500 12.500
430912 430.912
9123456 9.123.456
1111111111 1.111.111.111
81343902530 81.343.902.530
1111111111111 1.111.111.111.111
62123456789011 62.123.456.789.011
1111111111111111 1.111.111.111.111.111

One odd thing with the n operator is that when I didn’t specify a locale, it used nothing. I’m not sure why. Running locale.getlocale() definitely returned en_US, but maybe the expectation is that you should always set a locale when using it. I tried this and it worked:

locale.setlocale(locale.LC_ALL,locale.getlocale())

I’m chalking that up to something I did wrong, or misunderstood.

Ok, so that’s basic formatting, how would you do the nice ‘short’ format? Use the numerize library. You can find it here, https://github.com/davidsa03/numerize, and after installing it via pip, here’s an example of it in use:

from numerize.numerize import numerize # numbers defined here... for i in inputs: print(f"{i:<30}{numerize(i)}")

And the output:

999 999
1000 1K
2999 3K
12499 12.5K
12500 12.5K
430912 430.91K
9123456 9.12M
1111111111 1.11B
81343902530 81.34B
1111111111111 1.11T
62123456789011 62.12T
1111111111111111 1111111111111111

Noticed that it worked perfectly… except for the final huge number, but as I mentioned in the last post, JavaScript’s Intl also didn’t handle it exactly right, although I do think it handled it better, returning 1111T instead. Either way, numerize is pretty nifty and was quick to use.