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Editorial Team
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Asked: 2026-05-13T09:48:46+00:00

I always have to know why, rather than just how, so here I go:

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I always have to know why, rather than just how, so here I go:

How does this work:

'{0:01.2f}'.format(5.555)  #returns '5.55'

'{0:01.1f}'.format(5.555)  #returns '5.5'

'{0:1.2f}'.format(5.555)   #returns '5.55' again

'{0:1.1f}'.format(5.555)   #returns '5.5' again

Why does this not add zero padding by returning ‘05.5’ instead of just ‘5.5’ when I have the extra zero. It just doesn’t seem to work.

Also, why is the string 0:1.1f instead of 0:0.1f, etc. Is it just a convention to use the number 1 before the decimal instead of a zero, or is that the syntax?

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1 Answer

  1. Editorial Team

    Its because the 0 character enables zero-padding, but you have a width of 1 set. Set the width to 2 (like '{0:02.1f}' and you will see a leading 0.

    Edit – actually, I’m not sure if 2 will suffice, because I don’t know how it behaves with more digits after the decimal point. So to be safe, make it something like 5 and see what it does then.

    Edit 2 – ok, I just tried it. The width corresponds to the TOTAL width, including all digits and the decimal point. So you’ll get this:

    >>> '{0:05.2f}'.format(5.555)
'05.55'

    Note that the total length of the string is 5 now, with a leading 0 because zero-padding is enabled, and that it truncates to 2 digits after the decimal point because of .2

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