Support formatting floats in hexadecimal (and binary?) notation #113804
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type-feature
A feature request or enhancement
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skirpichev
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Jan 8, 2024
_Py_dg_dtoa_hex() is based on float.hex() with additional support for
the precision setting and some format flags.
Examples:
```pycon
>>> f'{-0.1:x}'
'-0x1.999999999999ap-4'
>>> (-0.1).hex()
'-0x1.999999999999ap-4'
>>> f'{3.14159:+X}'
'+0X1.921F9F01B866EP+1'
>>> f'{3.14159:.3x}'
'0x1.922p+1'
```
skirpichev
added a commit
to skirpichev/cpython
that referenced
this issue
Jan 8, 2024
_Py_dg_dtoa_hex() is based on float.hex() with additional support for
the precision setting and some format flags.
Examples:
```pycon
>>> f'{-0.1:x}'
'-0x1.999999999999ap-4'
>>> (-0.1).hex()
'-0x1.999999999999ap-4'
>>> f'{3.14159:+X}'
'+0X1.921F9F01B866EP+1'
>>> f'{3.14159:.3x}'
'0x1.922p+1'
```
skirpichev
added a commit
to skirpichev/cpython
that referenced
this issue
Jan 12, 2024
_Py_dg_dtoa_hex() helper is based on float.hex() with additional support
for the precision setting and some format flags. Note (c.f. ``'a'``
format type of the C stdlib), that ``'#'`` option is used to control the
prefix (off by default).
Trailing zeros (and the dot) in fractional part are excluded.
Examples:
```pycon
>>> f'{-0.1:#x}'
'-0x1.999999999999ap-4'
>>> (-0.1).hex()
'-0x1.999999999999ap-4'
>>> f'{3.14159:+#X}'
'+0X1.921F9F01B866EP+1'
>>> f'{3.14159:.3x}'
'1.922p+1'
```
Minor changes:
* added Py_hexdigits_upper constant
* tests for RaisingNumber are moved (to test also bytes)
|
PR is ready for review: #113805 |
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Feature or enhancement
Proposal:
Currently there is the
float.hex()method to get a representation of a floating-point number as a hexadecimal string.We can also (instead?) add same formating option for the
str.format(), f-strings and old-style ('%' operator) string formatting. The Cprintf()has a dedicated type fields for this: 'a' and 'A'. While it's possible to add such formatting types for thestr.format()as well, for the old-style string formatting these letters will conflict (see this) with theascii()conversion type. Lets instead reuse 'x' and 'X' type fields for this, currently supported only for integers.This proposal introduce an incompatibility with C-style
printf(), but some other languages also have such one. Notable example is the Go's fmt package.New interface for formatting of floats will be more flexible and compact than the former
float.hex():We may also consider to support printing floats as binary strings. Either in the base-2 scientific notation, or like the Go's strconv.FormatFloat.
Has this already been discussed elsewhere?
I have already discussed this feature proposal on Discourse
Links to previous discussion of this feature:
https://discuss.python.org/t/41848
Linked PRs
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