When installing certain libraries using pip in Python 3.15.0a2, pip reports an error

[HIbingai]

Bug report

Bug description:

When using “pip install ”, you may encounter the following error：

> Collecting numpy
  Using cached https://pypi.tuna.tsinghua.edu.cn/packages/76/65/21b3bc86aac7b8f2862db1e808f1ea22b028e30a225a34a5ede9bf8678f2/numpy-2.3.5.tar.gz (20.6 MB)
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
  Installing backend dependencies ... done
  Preparing metadata (pyproject.toml) ... error
  error: subprocess-exited-with-error

  × Preparing metadata (pyproject.toml) did not run successfully.
  │ exit code: 2
  ╰─> [89 lines of output]
      + C:\Users\47268\AppData\Local\Programs\Python\Python315\python.exe C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\meson.py setup C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153 C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\.mesonpy-1q31a28p -Dbuildtype=release -Db_ndebug=if-release -Db_vscrt=md --native-file=C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\.mesonpy-1q31a28p\meson-python-native-file.ini
      Exception in thread Thread-4 (_readerthread):
      Exception in thread Thread-3 (_readerthread):
      Traceback (most recent call last):
        File "C:\Users\47268\AppData\Local\Programs\Python\Python315\Lib\threading.py", line 1075, in _bootstrap_inner
          self._context.run(self.run)
          ~~~~~~~~~~~~~~~~~^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Programs\Python\Python315\Lib\threading.py", line 1017, in run
          self._target(*self._args, **self._kwargs)
          ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Programs\Python\Python315\Lib\subprocess.py", line 1612, in _readerthread
          buffer.append(fh.read())
                        ~~~~~~~^^
        File "<frozen codecs>", line 325, in decode
      UnicodeDecodeError: 'utf-8' codec can't decode byte 0xb1 in position 19: invalid start byte
      Traceback (most recent call last):
        File "C:\Users\47268\AppData\Local\Programs\Python\Python315\Lib\threading.py", line 1075, in _bootstrap_inner
          self._context.run(self.run)
          ~~~~~~~~~~~~~~~~~^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Programs\Python\Python315\Lib\threading.py", line 1017, in run
          self._target(*self._args, **self._kwargs)
          ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Programs\Python\Python315\Lib\subprocess.py", line 1612, in _readerthread
          buffer.append(fh.read())
                        ~~~~~~~^^
        File "<frozen codecs>", line 325, in decode
      UnicodeDecodeError: 'utf-8' codec can't decode byte 0xd3 in position 0: invalid continuation byte
      Traceback (most recent call last):
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\mesonmain.py", line 193, in run
          return options.run_func(options)
                 ~~~~~~~~~~~~~~~~^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\msetup.py", line 390, in run
          app.generate()
          ~~~~~~~~~~~~^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\msetup.py", line 192, in generate
          return self._generate(env, capture, vslite_ctx)
                 ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\msetup.py", line 232, in _generate
          intr = interpreter.Interpreter(b, user_defined_options=user_defined_options)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\interpreter\interpreter.py", line 308, in __init__
          self.parse_project()
          ~~~~~~~~~~~~~~~~~~^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\interpreterbase\interpreterbase.py", line 138, in parse_project
          self.evaluate_codeblock(self.ast, end=1)
          ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\interpreterbase\interpreterbase.py", line 203, in evaluate_codeblock
          raise e
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\interpreterbase\interpreterbase.py", line 195, in evaluate_codeblock
          self.evaluate_statement(cur)
          ~~~~~~~~~~~~~~~~~~~~~~~^^^^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\interpreterbase\interpreterbase.py", line 209, in evaluate_statement
          return self.function_call(cur)
                 ~~~~~~~~~~~~~~~~~~^^^^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\interpreterbase\interpreterbase.py", line 536, in function_call
          res = func(node, func_args, kwargs)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\interpreterbase\decorators.py", line 237, in wrapper
          return f(*nargs, **wrapped_kwargs)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\interpreterbase\decorators.py", line 556, in wrapper
          return f(*wrapped_args, **wrapped_kwargs)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\interpreter\interpreter.py", line 1293, in func_project
          self.add_languages(proj_langs, True, MachineChoice.HOST)
          ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\interpreter\interpreter.py", line 1477, in add_languages
          success = self.add_languages_for(args, required, for_machine)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\interpreter\interpreter.py", line 1520, in add_languages_for
          comp = compilers.detect_compiler_for(self.environment, lang, for_machine, skip_sanity_check, self.subproject)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\compilers\detect.py", line 106, in detect_compiler_for
          comp = compiler_from_language(env, lang, for_machine)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\compilers\detect.py", line 103, in compiler_from_language
          return lang_map[lang](env, for_machine) if lang in lang_map else None
                 ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\compilers\detect.py", line 633, in detect_c_compiler
          return _detect_c_or_cpp_compiler(env, 'c', for_machine)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\vendored-meson\meson\mesonbuild\compilers\detect.py", line 335, in _detect_c_or_cpp_compiler
          full_version = out.split('\n', 1)[0]
                         ^^^^^^^^^
      AttributeError: 'NoneType' object has no attribute 'split'
      The Meson build system
      Version: 1.8.3
      Source dir: C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153
      Build dir: C:\Users\47268\AppData\Local\Temp\pip-install-2f38qn8g\numpy_3ba56112f04847cc82d9e0eee045d153\.mesonpy-1q31a28p
      Build type: native build
      Activating VS 17.14.21 (November 2025)
      Project name: NumPy
      Project version: 2.3.5

      ..\meson.build:1:0: ERROR: Unhandled python exception

          This is a Meson bug and should be reported!
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> numpy

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.

D:\Users\47268\Downloads\Compressed\Tiemu-main>pip install numpy --only-binary=all --force-reinstall
Looking in indexes: https://pypi.tuna.tsinghua.edu.cn/simple
Collecting numpy
  Using cached https://pypi.tuna.tsinghua.edu.cn/packages/76/65/21b3bc86aac7b8f2862db1e808f1ea22b028e30a225a34a5ede9bf8678f2/numpy-2.3.5.tar.gz (20.6 MB)
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
  Installing backend dependencies ... done
  Preparing metadata (pyproject.toml) ... error
  error: subprocess-exited-with-error

  × Preparing metadata (pyproject.toml) did not run successfully.
  │ exit code: 2
  ╰─> [89 lines of output]
      + C:\Users\47268\AppData\Local\Programs\Python\Python315\python.exe C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\meson.py setup C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4 C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\.mesonpy-knf3eg74 -Dbuildtype=release -Db_ndebug=if-release -Db_vscrt=md --native-file=C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\.mesonpy-knf3eg74\meson-python-native-file.ini
      Exception in thread Thread-4 (_readerthread):
      Exception in thread Thread-3 (_readerthread):
      Traceback (most recent call last):
        File "C:\Users\47268\AppData\Local\Programs\Python\Python315\Lib\threading.py", line 1075, in _bootstrap_inner
          self._context.run(self.run)
          ~~~~~~~~~~~~~~~~~^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Programs\Python\Python315\Lib\threading.py", line 1017, in run
          self._target(*self._args, **self._kwargs)
          ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Programs\Python\Python315\Lib\subprocess.py", line 1612, in _readerthread
          buffer.append(fh.read())
                        ~~~~~~~^^
        File "<frozen codecs>", line 325, in decode
      UnicodeDecodeError: 'utf-8' codec can't decode byte 0xb1 in position 19: invalid start byte
      Traceback (most recent call last):
        File "C:\Users\47268\AppData\Local\Programs\Python\Python315\Lib\threading.py", line 1075, in _bootstrap_inner
          self._context.run(self.run)
          ~~~~~~~~~~~~~~~~~^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Programs\Python\Python315\Lib\threading.py", line 1017, in run
          self._target(*self._args, **self._kwargs)
          ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Programs\Python\Python315\Lib\subprocess.py", line 1612, in _readerthread
          buffer.append(fh.read())
                        ~~~~~~~^^
        File "<frozen codecs>", line 325, in decode
      UnicodeDecodeError: 'utf-8' codec can't decode byte 0xd3 in position 0: invalid continuation byte
      Traceback (most recent call last):
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\mesonmain.py", line 193, in run
          return options.run_func(options)
                 ~~~~~~~~~~~~~~~~^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\msetup.py", line 390, in run
          app.generate()
          ~~~~~~~~~~~~^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\msetup.py", line 192, in generate
          return self._generate(env, capture, vslite_ctx)
                 ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\msetup.py", line 232, in _generate
          intr = interpreter.Interpreter(b, user_defined_options=user_defined_options)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\interpreter\interpreter.py", line 308, in __init__
          self.parse_project()
          ~~~~~~~~~~~~~~~~~~^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\interpreterbase\interpreterbase.py", line 138, in parse_project
          self.evaluate_codeblock(self.ast, end=1)
          ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\interpreterbase\interpreterbase.py", line 203, in evaluate_codeblock
          raise e
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\interpreterbase\interpreterbase.py", line 195, in evaluate_codeblock
          self.evaluate_statement(cur)
          ~~~~~~~~~~~~~~~~~~~~~~~^^^^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\interpreterbase\interpreterbase.py", line 209, in evaluate_statement
          return self.function_call(cur)
                 ~~~~~~~~~~~~~~~~~~^^^^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\interpreterbase\interpreterbase.py", line 536, in function_call
          res = func(node, func_args, kwargs)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\interpreterbase\decorators.py", line 237, in wrapper
          return f(*nargs, **wrapped_kwargs)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\interpreterbase\decorators.py", line 556, in wrapper
          return f(*wrapped_args, **wrapped_kwargs)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\interpreter\interpreter.py", line 1293, in func_project
          self.add_languages(proj_langs, True, MachineChoice.HOST)
          ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\interpreter\interpreter.py", line 1477, in add_languages
          success = self.add_languages_for(args, required, for_machine)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\interpreter\interpreter.py", line 1520, in add_languages_for
          comp = compilers.detect_compiler_for(self.environment, lang, for_machine, skip_sanity_check, self.subproject)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\compilers\detect.py", line 106, in detect_compiler_for
          comp = compiler_from_language(env, lang, for_machine)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\compilers\detect.py", line 103, in compiler_from_language
          return lang_map[lang](env, for_machine) if lang in lang_map else None
                 ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\compilers\detect.py", line 633, in detect_c_compiler
          return _detect_c_or_cpp_compiler(env, 'c', for_machine)
        File "C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\vendored-meson\meson\mesonbuild\compilers\detect.py", line 335, in _detect_c_or_cpp_compiler
          full_version = out.split('\n', 1)[0]
                         ^^^^^^^^^
      AttributeError: 'NoneType' object has no attribute 'split'
      The Meson build system
      Version: 1.8.3
      Source dir: C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4
      Build dir: C:\Users\47268\AppData\Local\Temp\pip-install-7kz9ss7e\numpy_dce3a841859043398712e498227031b4\.mesonpy-knf3eg74
      Build type: native build
      Activating VS 17.14.21 (November 2025)
      Project name: NumPy
      Project version: 2.3.5

      ..\meson.build:1:0: ERROR: Unhandled python exception

          This is a Meson bug and should be reported!
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> numpy

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.

CPython versions tested on:

3.15

Operating systems tested on:

Windows

[hugovk]

This is because NumPy doesn't yet have prebuilt binary wheels for Python 3.15: see https://pypi.org/project/numpy/#files (and I expect the same for the https://mirrors.tuna.tsinghua.edu.cn mirror). It's too early for them to provide them, I think they typically wait until around beta in May. So pip is trying to build from source, but you don't have all the dependencies set up.

I recommend using 3.14 with NumPy, or checking NumPy docs for how to build from source on Windows.

[terryjreedy]

Perhaps our download pages, especially for previews, should mention what error is displayed when a package is not available. Even better would be if pip/meson said something better than requesting a bogus report: "This is a Meson bug and should be reported!".