[3.10] bpo-43945: [Enum] reduce scope of new format() behavior (GH-26752)
* [Enum] reduce scope of new format behavior
Instead of treating all Enums the same for format(), only user mixed-in
enums will be affected. In other words, IntEnum and IntFlag will not be
changing the format() behavior, due to the requirement that they be
drop-in replacements of existing integer constants.
If a user creates their own integer-based enum, then the new behavior
will apply:
class Grades(int, Enum):
A = 5
B = 4
C = 3
D = 2
F = 0
Now: format(Grades.B) -> DeprecationWarning and '4'
3.12: -> no warning, and 'B'.
(cherry picked from commit f60b07ab6c943fce084772c3c7731ab3bbd213ff)
Co-authored-by: Ethan Furman <ethan@stoneleaf.us>diff --git a/Lib/enum.py b/Lib/enum.py
index 9077798..84e3cc1 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -993,9 +993,9 @@ def __format__(self, format_spec):
# mixed-in Enums should use the mixed-in type's __format__, otherwise
# we can get strange results with the Enum name showing up instead of
# the value
-
+ #
# pure Enum branch, or branch with __str__ explicitly overridden
- str_overridden = type(self).__str__ not in (Enum.__str__, Flag.__str__)
+ str_overridden = type(self).__str__ not in (Enum.__str__, IntEnum.__str__, Flag.__str__)
if self._member_type_ is object or str_overridden:
cls = str
val = str(self)
@@ -1005,7 +1005,7 @@ def __format__(self, format_spec):
import warnings
warnings.warn(
"in 3.12 format() will use the enum member, not the enum member's value;\n"
- "use a format specifier, such as :d for an IntEnum member, to maintain "
+ "use a format specifier, such as :d for an integer-based Enum, to maintain "
"the current display",
DeprecationWarning,
stacklevel=2,
@@ -1044,6 +1044,22 @@ class IntEnum(int, Enum):
Enum where members are also (and must be) ints
"""
+ def __str__(self):
+ return "%s" % (self._name_, )
+
+ def __format__(self, format_spec):
+ """
+ Returns format using actual value unless __str__ has been overridden.
+ """
+ str_overridden = type(self).__str__ != IntEnum.__str__
+ if str_overridden:
+ cls = str
+ val = str(self)
+ else:
+ cls = self._member_type_
+ val = self._value_
+ return cls.__format__(val, format_spec)
+
class StrEnum(str, Enum):
"""
@@ -1072,6 +1088,8 @@ def __new__(cls, *values):
__str__ = str.__str__
+ __format__ = str.__format__
+
def _generate_next_value_(name, start, count, last_values):
"""
Return the lower-cased version of the member name.
@@ -1300,6 +1318,16 @@ class IntFlag(int, Flag, boundary=EJECT):
Support for integer-based Flags
"""
+ def __format__(self, format_spec):
+ """
+ Returns format using actual value unless __str__ has been overridden.
+ """
+ str_overridden = type(self).__str__ != Flag.__str__
+ value = self
+ if not str_overridden:
+ value = self._value_
+ return int.__format__(value, format_spec)
+
def __or__(self, other):
if isinstance(other, self.__class__):
other = other._value_