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Rodrigo Girão Serrão: TIL #134 – = alignment in string formatting

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Today I learned how to use the equals sign to align numbers when doing string formatting in Python.

There are three main alignment options in Python's string formatting:

However, numbers have a fourth option=. On the surface, it looks like it doesn't do anything:

x = 73 print(f"@{x:10}@") # @ 73@ print(f"@{x:=10}@") # @ 73@

But that's because=influences the alignment of the sign. If I makexnegative, we already see something:

x = -73 print(f"@{x:10}@") # @ -73@ print(f"@{x:=10}@") # @- 73@

So, the equals sign=aligns a number to the right but aligns its sign to the left. That may look weird, but I guess that's useful if you want to pad a number with 0s:

x = -73 print(f"@{x:010}@") # @-000000073@

In fact, there is a shortcut for this type of alignment, which is to just put a zero immediately to the left of the width when aligning a number:

x = -73 print(f"@{x:010}@") # @-000000073@

The zero immediately to the left changes the default alignment of numbers to be=instead of>.

https://mathspp.com/blog/til/-alignment-in-string-formatting

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