use lowercase letters for digits

[fametrano]

Black standardizes most numeric literals to use lowercase letters for the syntactic parts and uppercase letters for the digits themselves. The uppercase choice decreases readability for hexadecimal numbers, mostly because A is very similar to 4.
Please consider using lowercase letters for both the syntactic parts and the digits themselves.

0xAA44A4A4
vs
0xaa44a4a4

[zsol]

#1692 is a duplicate of this one, but it has a bit more context and discussion, so closing this in favor of that.