`~bool` deprecation not reported for literals #134280

decorator-factory · 2025-05-19T20:47:28Z

Bug report

Bug description:

Related to: #103487

# literal.py
print(~False)
print(~True)

# var.py
a = True
print(~a)

b = False
print(~b)

A DeprecationWarning is reported for var.py, but not for literal.py.

$ python -c 'import sys; print(sys.version)'
3.15.0a0 (heads/main:42d03f3, May 19 2025, 23:32:01) [GCC 15.1.1 20250425 (Red Hat 15.1.1-1)]

$ python literal.py
-1
-2

$ python var.py
/tmp/scratch/var.py:2: DeprecationWarning: Bitwise inversion '~' on bool is deprecated and will be removed in Python 3.16. This returns the bitwise inversion of the underlying int object and is usually not what you expect from negating a bool. Use the 'not' operator for boolean negation or ~int(x) if you really want the bitwise inversion of the underlying int.
  print(~a)
-2
/tmp/scratch/var.py:5: DeprecationWarning: Bitwise inversion '~' on bool is deprecated and will be removed in Python 3.16. This returns the bitwise inversion of the underlying int object and is usually not what you expect from negating a bool. Use the 'not' operator for boolean negation or ~int(x) if you really want the bitwise inversion of the underlying int.
  print(~b)
-1

What's interesting is that there's a test for this:

cpython/Lib/test/test_bool.py

Lines 68 to 71 in 42d03f3

    
           with self.assertWarns(DeprecationWarning): 
        
               # also check that the warning is issued in case of constant 
        
               # folding at compile time 
        
               self.assertEqual(eval("~False"), -1)

and the DeprecationWarning is raised if eval("~True") is used instead of just ~True

$ python -c 'print(~True)'
-2
$ python -c 'print(eval("~True"))'
<string>:1: DeprecationWarning: Bitwise inversion '~' on bool is deprecated and will be removed in Python 3.16. This returns the bitwise inversion of the underlying int object and is usually not what you expect from negating a bool. Use the 'not' operator for boolean negation or ~int(x) if you really want the bitwise inversion of the underlying int.
-2

CPython versions tested on:

CPython main branch, 3.13

Operating systems tested on:

Linux

Linked PRs

gh-134280: Disable constant folding for ~ with a boolean argument #134982

The text was updated successfully, but these errors were encountered:

StanFromIreland · 2025-05-19T21:20:38Z

It seems to warn for me on 3.15 and 3.14:

$ python3.15 -c 'print(~True)'
<sys>:0: DeprecationWarning: Bitwise inversion '~' on bool is deprecated and will be removed in Python 3.16. This returns the bitwise inversion of the underlying int object and is usually not what you expect from negating a bool. Use the 'not' operator for boolean negation or ~int(x) if you really want the bitwise inversion of the underlying int.
-2

This is 3.13 only.

decorator-factory · 2025-05-19T21:38:13Z

@StanFromIreland I ran it in a container (https://hub.docker.com/_/python/) on 3.14 for reproducibility:

$ podman run -ti --rm python:3.14.0b1-slim bash
root@a9edb8be24cb:/# python -c 'print(~True)'
-2
root@a9edb8be24cb:/# python -c 'print(eval("~True"))'
<string>:1: DeprecationWarning: Bitwise inversion '~' on bool is deprecated and will be removed in Python 3.16. This returns the bitwise inversion of the underlying int object and is usually not what you expect from negating a bool. Use the 'not' operator for boolean negation or ~int(x) if you really want the bitwise inversion of the underlying int.
-2
root@a9edb8be24cb:/# python
Python 3.14.0b1 (main, May  9 2025, 23:49:24) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> ~True
-2
>>> ~False
-1
>>>

On 3.15 in debug mode, I do get a warning:

$ ./configure --with-pydebug
...
$ make -j 12
...
$ ./python -c 'print(~True)'
<sys>:0: DeprecationWarning: Bitwise inversion '~' on bool is deprecated and will be removed in Python 3.16. This returns the bitwise inversion of the underlying int object and is usually not what you expect from negating a bool. Use the 'not' operator for boolean negation or ~int(x) if you really want the bitwise inversion of the underlying int.
-2
$ ./python
Python 3.15.0a0 (heads/main:42d03f3, May 20 2025, 00:35:04) [GCC 15.1.1 20250425 (Red Hat 15.1.1-1)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> ~True
/home/df/clones/cpython/Lib/codeop.py:117: DeprecationWarning: Bitwise inversion '~' on bool is deprecated and will be removed in Python 3.16. This returns the bitwise inversion of the underlying int object and is usually not what you expect from negating a bool. Use the 'not' operator for boolean negation or ~int(x) if you really want the bitwise inversion of the underlying int.
  codeob = compile(source, filename, symbol, flags, True)
-2
>>>

EDIT: seems like the warning is displayed in 3.13 and 3.14 if the -X dev flag is enabled

AA-Turner · 2025-05-20T02:35:37Z

cc @timhoffm

timhoffm · 2025-05-20T04:52:17Z

I will look into this.

serhiy-storchaka · 2025-05-31T10:34:44Z

This works as intended. By default, DeprecationWarning is only reported for the __main__ module in the Python development mode or in the debug build.

Run Python with -W always or -X dev to see them.

decorator-factory · 2025-05-31T14:16:28Z

So in this case, the operation is considered to be in the __main__ module

if __name__ == "__main__":
    a = True
    print(~a)  # prints -2, with DeprecationWarning

but here it's considered to be outside of __main__?

if __name__ == "__main__":
    print(~True)  # prints -2, no DeprecationWarning

(from the docs (https://docs.python.org/3/library/exceptions.html#DeprecationWarning) and PEP 565 I'm assuming that you meant that deprecation warnings are only active in __main__ by default

default::DeprecationWarning:__main__
ignore::DeprecationWarning
ignore::PendingDeprecationWarning
ignore::ImportWarning
ignore::BytesWarning
ignore::ResourceWarning

)

serhiy-storchaka · 2025-05-31T15:56:15Z

Well, this is obviously related to the fact that ~True is calculated at the compile time.

If warnings are ignored in the constant folding, this is a bug.

This moves the deprecation warning from compile time to runtime.

serhiy-storchaka · 2025-05-31T17:00:51Z

#134982 disables constant folding for ~bool. This moves the deprecation warning from compile time to runtime.

Ideally, we could also emit a SyntaxWarning at compile time, like we do for ()(), but this is rather an additional feature with low benefit/cost ratio.

We narrowly avoided a bullet with not NotImplemented.

decorator-factory added the type-bug An unexpected behavior, bug, or error label May 19, 2025

picnixz added the interpreter-core (Objects, Python, Grammar, and Parser dirs) label May 19, 2025

AA-Turner added 3.13 bugs and security fixes 3.14 bugs and security fixes 3.15 new features, bugs and security fixes labels May 20, 2025

serhiy-storchaka added the pending The issue will be closed if no feedback is provided label May 31, 2025

serhiy-storchaka self-assigned this May 31, 2025

serhiy-storchaka removed the pending The issue will be closed if no feedback is provided label May 31, 2025

serhiy-storchaka added a commit to serhiy-storchaka/cpython that referenced this issue May 31, 2025

pythongh-134280: Disable constant folding for ~ with a boolean argument

deb1724

This moves the deprecation warning from compile time to runtime.

bedevere-app bot mentioned this issue May 31, 2025

gh-134280: Disable constant folding for ~ with a boolean argument #134982

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`~bool` deprecation not reported for literals #134280

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Bug report

Bug description:

CPython versions tested on:

Operating systems tested on:

Linked PRs

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`~bool` deprecation not reported for literals #134280

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