f-string formatting: display number sign?

Basic question about python f-strings, but couldn't find out the answer: how to force sign display of a float or integer number? i.e. what f-string makes 3 displayed as +3?

From Docs:

• Format Specification Mini-Language(Emphasis mine):

Option	Meaning
'+'	indicates that a sign should be used for both positive as well as negative numbers.
'-'	indicates that a sign should be used only for negative numbers (this is the default behavior).

Example from docs:

>>> '{:+f}; {:+f}'.format(3.14, -3.14)  # show it always
'+3.140000; -3.140000'
>>> '{:-f}; {:-f}'.format(3.14, -3.14)  # show only the minus -- same as '{:f}; {:f}'
'3.140000; -3.140000'
>>> '{:+} {:+}'.format(10, -10)
'+10 -10'

Above examples using f-strings:

>>> f'{3.14:+f}; {-3.14:+f}'
'+3.140000; -3.140000'
>>> f'{3.14:-f}; {-3.14:-f}'
'3.140000; -3.140000'
>>> f'{10:+} {-10:+}'
'+10 -10'

One caveat while printing 0 as 0 is neither positive nor negative. In python, +0 = -0 = 0.

>>> f'{0:+} {-0:+}'
'+0 +0'
>>> f'{0.0:+} {-0.0:+}'
'+0.0 -0.0'

0.0 and -0.0 are different objects¹.

• 0 in Computer Science(Emphasis mine):

In some computer hardware signed number representations, zero has two distinct representations, a positive one grouped with the positive numbers and a negative one grouped with the negatives; this kind of dual representation is known as signed zero, with the latter form sometimes called negative zero.

Update: From Python 3.11 and above, allows negative floating point zero as positive zero.

The 'z' option coerces negative zero floating-point values to positive zero after rounding to the format precision. This option is only valid for floating-point presentation types.

Example from PEP682:

>>> x = -.00001
>>> f'{x:z.1f}' '0.0'

>>> x = decimal.Decimal('-.00001')
>>> '{:+z.1f}'.format(x) '+0.0' 

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_{1. Negative 0 in Python. Also check out Signed Zero (-0)}