[issue37427] sorted() and list.sort() don't accept non-boolean objects with __bool__() as `reverse` parameter

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

See issue15999.

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nosy: +serhiy.storchaka

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[issue37427] sorted() and list.sort() don't accept non-boolean objects with __bool__() as `reverse` parameter

[Mark Dickinson]

Mark Dickinson  added the comment:

> I'm finding it rather hard to guess what the rules are for what works and 
> what doesn't

So now that I've looked at the source: anything with an `__int__` method works, 
except that `float` instances are explicitly excluded. So this explains for 
example:

>>> sorted([1, 2, 3], reverse=numpy.float64(0.5))
Traceback (most recent call last):
  File "", line 1, in 
TypeError: integer argument expected, got float
>>> sorted([1, 2, 3], reverse=numpy.float32(0.5))
[1, 2, 3]

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[issue37427] sorted() and list.sort() don't accept non-boolean objects with __bool__() as `reverse` parameter

[Mark Dickinson]

Change by Mark Dickinson :


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nosy: +tim.peters

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[issue37427] sorted() and list.sort() don't accept non-boolean objects with __bool__() as `reverse` parameter

[Mark Dickinson]

Mark Dickinson  added the comment:

I haven't looked at the source yet, but from experimentation I'm finding it 
rather hard to guess what the rules are for what works and what doesn't:

Python 3.7.3 (default, Mar 30 2019, 03:37:43) 
[Clang 10.0.0 (clang-1000.11.45.5)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import decimal, fractions, numpy
>>> sorted([1, 2, 3], reverse=0.5)
Traceback (most recent call last):
  File "", line 1, in 
TypeError: integer argument expected, got float
>>> sorted([1, 2, 3], reverse=decimal.Decimal(0.5))
[1, 2, 3]
>>> sorted([1, 2, 3], reverse=fractions.Fraction(0.5))
Traceback (most recent call last):
  File "", line 1, in 
TypeError: an integer is required (got type Fraction)
>>> sorted([1, 2, 3], reverse=numpy.int64(1))
[3, 2, 1]
>>> sorted([1, 2, 3], reverse=numpy.bool_(True))
[3, 2, 1]

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[issue37427] sorted() and list.sort() don't accept non-boolean objects with __bool__() as `reverse` parameter

[Karthikeyan Singaravelan]

Change by Karthikeyan Singaravelan :


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[issue37427] sorted() and list.sort() don't accept non-boolean objects with __bool__() as `reverse` parameter

[NODA, Kai]

New submission from NODA, Kai :

class X:
def __bool__(self):
return True

x = [1, 2, 3]
x.sort(reverse=X())
print(x)
print(sorted([1, 2, 3], reverse=X()))

TypeError: an integer is required (got type X)

We can always still do

x.sort(reverse=bool(X()))
print(sorted([1, 2, 3], reverse=bool(X(

but that isn't cool

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components: Interpreter Core
messages: 346722
nosy: nodakai
priority: normal
severity: normal
status: open
title: sorted() and list.sort() don't accept non-boolean objects with 
__bool__() as `reverse` parameter
type: behavior
versions: Python 3.9

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