Peter Bengtsson: Format thousands in Python

tl;dr; Usee f"{number:,}" to thousands format an integer to a string.

I keep forgetting and having to look this up every time. Hopefully by blogging about it, this time it'll stick in my memory. And hopefully in yours too :)

Suppose you have a number, like 1234567890 and you want to display it, here's how you do it:

>>> number = 1234567890
>>> f"{number:,}"
'1,234,567,890'

In the past, before Python 3.6, I've been using:

>>> number = 1234567890
>>> format(number, ",")
'1,234,567,890'

All of this and more detail can be found in PEP 378 -- Format Specifier for Thousands Separator. For example, you can do this beast too:

>>> number = 1234567890
>>> f"{number:020,.2f}"
'0,001,234,567,890.00'

which demonstrates (1) how to do zero-padding (of length 20), (2) the thousands comma, (3) round to 2 significant figures. All useful weapons to be able to draw from the top of your head.

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