Dim sort

CHANGES

@@ -4,7 +4,9 @@ Pint Changelog
 0.24 (unreleased)
 -----------------
 
-- Nothing changed yet.
+- Add `dim_sort` function to _formatter_helpers.
+- Add `dim_order` and `default_sort_func` properties to FullFormatter.
+ (PR #1926, fixes Issue #1841)
 
 
 0.23 (2023-12-08)

pint/delegates/formatter/_format_helpers.py

@@ -265,9 +265,67 @@ def format_compound_unit(
  if locale is not None:
  out = localized_form(out, use_plural, length or "long", locale)
 
+ if registry:
+ out = registry.formatter.default_sort_func(out, registry)
+
  return out
 
 
+def dim_sort(items: Iterable[tuple[str, Number]], registry: UnitRegistry):
+ """Sort a list of units by dimensional order (from `registry.formatter.dim_order`).
+
+ Parameters
+ ----------
+ items : tuple
+ a list of tuples containing (unit names, exponent values).
+ registry : UnitRegistry
+ the registry to use for looking up the dimensions of each unit.
+
+ Returns
+ -------
+ list
+ the list of units sorted by most significant dimension first.
+
+ Raises
+ ------
+ KeyError
+ If unit cannot be found in the registry.
+ """
+
+ if registry is None:
+ return items
+ ret_dict = dict()
+ dim_order = registry.formatter.dim_order
+ for unit_name, unit_exponent in items:
+ cname = registry.get_name(unit_name)
+ if not cname:
+ continue
+ cname_dims = registry.get_dimensionality(cname)
+ if len(cname_dims) == 0:
+ cname_dims = {"[]": None}
+ dim_types = iter(dim_order)
+ while True:
+ try:
+ dim = next(dim_types)
+ if dim in cname_dims:
+ if dim not in ret_dict:
+ ret_dict[dim] = list()
+ ret_dict[dim].append(
+ (
+ unit_name,
+ unit_exponent,
+ )
+ )
+ break
+ except StopIteration:
+ raise KeyError(
+ f"Unit {unit_name} (aka {cname}) has no recognized dimensions"
+ )
+
+ ret = sum([ret_dict[dim] for dim in dim_order if dim in ret_dict], [])
+ return ret
+
+
 def formatter(
  items: Iterable[tuple[str, Number]],
  as_ratio: bool = True,
@@ -309,6 +367,8 @@ def formatter(
  (Default value = lambda x: f"{x:n}")
  sort : bool, optional
  True to sort the formatted units alphabetically (Default value = True)
+ sort_func : callable
+ If not None, `sort_func` returns its sorting of the formatted units
 
  Returns
  -------
@@ -320,14 +380,14 @@ def formatter(
  if sort is False:
  warn(
  "The boolean `sort` argument is deprecated. "
- "Use `sort_fun` to specify the sorting function (default=sorted) "
+ "Use `sort_func` to specify the sorting function (default=sorted) "
  "or None to keep units in the original order."
  )
  sort_func = None
  elif sort is True:
  warn(
  "The boolean `sort` argument is deprecated. "
- "Use `sort_fun` to specify the sorting function (default=sorted) "
+ "Use `sort_func` to specify the sorting function (default=sorted) "
  "or None to keep units in the original order."
  )
  sort_func = sorted

pint/delegates/formatter/full.py

@@ -11,9 +11,9 @@
 
 from __future__ import annotations
 
-from typing import TYPE_CHECKING, Literal, Optional, Any
+from typing import TYPE_CHECKING, Callable, Iterable, Literal, Optional, Any
 import locale
-from ...compat import babel_parse, Unpack
+from ...compat import babel_parse, Number, Unpack
 from ...util import iterable
 
 from ..._typing import Magnitude
@@ -24,7 +24,12 @@
 from ._to_register import REGISTERED_FORMATTERS
 
 if TYPE_CHECKING:
- from ...facets.plain import PlainQuantity, PlainUnit, MagnitudeT
+ from ...facets.plain import (
+ GenericPlainRegistry,
+ PlainQuantity,
+ PlainUnit,
+ MagnitudeT,
+ )
  from ...facets.measurement import Measurement
  from ...compat import Locale
 
@@ -38,6 +43,23 @@ class FullFormatter:
  _formatters: dict[str, Any] = {}
 
  default_format: str = ""
+ # TODO: This can be over-riden by the registry definitions file
+ dim_order = (
+ "[substance]",
+ "[mass]",
+ "[current]",
+ "[luminosity]",
+ "[length]",
+ "[]",
+ "[time]",
+ "[temperature]",
+ )
+ default_sort_func: Optional[
+ Callable[
+ [Iterable[tuple[str, Number]], GenericPlainRegistry],
+ Iterable[tuple[str, Number]],
+ ]
+ ] = lambda self, x, registry: sorted(x)
 
  locale: Optional[Locale] = None
  babel_length: Literal["short", "long", "narrow"] = "long"

pint/delegates/formatter/html.py

@@ -78,7 +78,6 @@ def format_unit(
  self, unit: PlainUnit, uspec: str = "", **babel_kwds: Unpack[BabelKwds]
  ) -> str:
  units = format_compound_unit(unit, uspec, **babel_kwds)
-
  return formatter(
  units,
  as_ratio=True,
@@ -87,6 +86,7 @@ def format_unit(
  division_fmt=r"{}/{}",
  power_fmt=r"{}<sup>{}</sup>",
  parentheses_fmt=r"({})",
+ sort_func=None,
  )
 
  def format_quantity(

pint/delegates/formatter/latex.py

@@ -183,6 +183,7 @@ def format_unit(
  division_fmt=r"\frac[{}][{}]",
  power_fmt="{}^[{}]",
  parentheses_fmt=r"\left({}\right)",
+ sort_func=None,
  )
  return formatted.replace("[", "{").replace("]", "}")
 

pint/delegates/formatter/plain.py

@@ -77,6 +77,7 @@ def format_unit(
  division_fmt=" / ",
  power_fmt="{} ** {}",
  parentheses_fmt=r"({})",
+ sort_func=None,
  )
 
  def format_quantity(
@@ -175,6 +176,7 @@ def format_unit(
  division_fmt="/",
  power_fmt="{}**{}",
  parentheses_fmt=r"({})",
+ sort_func=None,
  )
 
  def format_quantity(
@@ -259,7 +261,6 @@ def format_unit(
  self, unit: PlainUnit, uspec: str = "", **babel_kwds: Unpack[BabelKwds]
  ) -> str:
  units = format_compound_unit(unit, uspec, **babel_kwds)
-
  return formatter(
  units,
  as_ratio=True,
@@ -269,6 +270,7 @@ def format_unit(
  power_fmt="{}{}",
  parentheses_fmt="({})",
  exp_call=pretty_fmt_exponent,
+ sort_func=None,
  )
 
  def format_quantity(

pint/testsuite/test_issues.py

@@ -1155,3 +1155,47 @@ def test_issues_1505():
  assert isinstance(
  ur.Quantity("m/s").magnitude, decimal.Decimal
  ) # unexpected fail (magnitude should be a decimal)
+
+
+def test_issues_1841(subtests):
+ from pint.delegates.formatter._format_helpers import dim_sort
+
+ ur = UnitRegistry()
+ ur.formatter.default_sort_func = dim_sort
+
+ for x, spec, result in (
+ (ur.Unit(UnitsContainer(hour=1, watt=1)), "P~", "W·h"),
+ (ur.Unit(UnitsContainer(ampere=1, volt=1)), "P~", "V·A"),
+ (ur.Unit(UnitsContainer(meter=1, newton=1)), "P~", "N·m"),
+ ):
+ with subtests.test(spec):
+ ur.default_format = spec
+ assert f"{x}" == result, f"Failed for {spec}, {result}"
+
+
+@pytest.mark.xfail
+def test_issues_1841_xfail():
+ from pint import formatting as fmt
+ from pint.delegates.formatter._format_helpers import dim_sort
+
+ # sets compact display mode by default
+ ur = UnitRegistry()
+ ur.default_format = "~P"
+ ur.formatter.default_sort_func = dim_sort
+
+ q = ur.Quantity("2*pi radian * hour")
+
+ # Note that `radian` (and `bit` and `count`) are treated as dimensionless.
+ # And note that dimensionless quantities are stripped by this process,
+ # leading to errorneous output. Suggestions?
+ assert (
+ fmt.format_unit(q.u._units, spec="", registry=ur, sort_dims=True)
+ == "radian * hour"
+ )
+ assert (
+ fmt.format_unit(q.u._units, spec="", registry=ur, sort_dims=False)
+ == "hour * radian"
+ )
+
+ # this prints "2*pi hour * radian", not "2*pi radian * hour" unless sort_dims is True
+ # print(q)