Bug in format specification in Python 3?

[Robert Dailey]

Hello,

According to the Python 3.1 documentation, I can have a format
specification like so:

print( 'This is a hex number: {:#08x}'.format( 4 ) )

This will print:

This is a hex number: 0x000004

I notice that the '0x' portion is counted in the width, which was
specified as 8. This seems wrong to me. Is this by design? If so, why?
I expect that the width portion to only apply to the input + padding
only. I don't consider the '0x' portion part of the padding. But maybe
it is...

 

[MRAB]

Hello,

According to the Python 3.1 documentation, I can have a format
specification like so:

print( 'This is a hex number: {:#08x}'.format( 4 ) )

This will print:

This is a hex number: 0x000004

I notice that the '0x' portion is counted in the width, which was
specified as 8. This seems wrong to me. Is this by design? If so, why?
I expect that the width portion to only apply to the input + padding
only. I don't consider the '0x' portion part of the padding. But maybe
it is...

The width portion is the width of what is produced by the specification.
The '#' tells it to add '0x', so that's part of what's produced. If you
don't want the '0x' to be counted then don't include '#' in the
specification. It makes perfect sense!

 

[AggieDan04]

Hello,

According to the Python 3.1 documentation, I can have a format
specification like so:

print( 'This is a hex number: {:#08x}'.format( 4 ) )

This will print:

This is a hex number: 0x000004

I notice that the '0x' portion is counted in the width, which was
specified as 8. This seems wrong to me. Is this by design? If so, why?
I expect that the width portion to only apply to the input + padding
only. I don't consider the '0x' portion part of the padding. But maybe
it is...

It's unintuitive to me, too, but it's the same thing that Python 2.x
did:
0x000004

 

[greg]

I notice that the '0x' portion is counted in the width, which was
specified as 8. This seems wrong to me. Is this by design? If so, why?

Yes, it's the total field width. This is consistent with
the other formats, in which it includes decimal points,
signs, etc.

If you don't want that, then write the format string as

'This is a hex number: 0x{:08x}'