无法使用 Python 3.9 venv `pip install numpy`

Question

我安装了 Python 3.9，创建了一个 venv 并尝试安装 numpy。 Cython 有一个错误，已在主干中修复。

所以我安装了 venv Cython 3.0a0 并重试：

(venv) marco@buzz:~/sources/cython$ pip install numpy --no-cache-dir

[...]

Collecting Cython>=0.29.13

[...]

ERROR: Command errored out with exit status 1: /home/marco/sources/tests/more_itertools/venv/bin/python3.9 /home/marco/sources/tests/more_itertools/venv/lib/python3.9/site-packages/pip install --ignore-installed --no-user --prefix /tmp/pip-build-env-3ctn3kl8/overlay --no-warn-script-location --no-binary :none: --only-binary :none: -i https://pypi.org/simple -- setuptools wheel 'Cython>=0.29.13' Check the logs for full command output.

所以我尝试在函数def install_requirements中注释掉venv/lib/python3.9/site-packages/pip/_internal/build_env.py中的--ignore-installed。我收到此错误：

ERROR: Exception:
Traceback (most recent call last):
  File "/home/marco/sources/tests/more_itertools/venv/lib/python3.9/site-packages/pip/_internal/cli/base_command.py", line 153, in _main
    status = self.run(options, args)
  File "/home/marco/sources/tests/more_itertools/venv/lib/python3.9/site-packages/pip/_internal/commands/install.py", line 382, in run
    resolver.resolve(requirement_set)
  File "/home/marco/sources/tests/more_itertools/venv/lib/python3.9/site-packages/pip/_internal/legacy_resolve.py", line 201, in resolve
    self._resolve_one(requirement_set, req)
  File "/home/marco/sources/tests/more_itertools/venv/lib/python3.9/site-packages/pip/_internal/legacy_resolve.py", line 365, in _resolve_one
    abstract_dist = self._get_abstract_dist_for(req_to_install)
  File "/home/marco/sources/tests/more_itertools/venv/lib/python3.9/site-packages/pip/_internal/legacy_resolve.py", line 312, in _get_abstract_dist_for
    abstract_dist = self.preparer.prepare_linked_requirement(
  File "/home/marco/sources/tests/more_itertools/venv/lib/python3.9/site-packages/pip/_internal/operations/prepare.py", line 223, in prepare_linked_requirement
    abstract_dist = _get_prepared_distribution(
  File "/home/marco/sources/tests/more_itertools/venv/lib/python3.9/site-packages/pip/_internal/operations/prepare.py", line 49, in _get_prepared_distribution
    abstract_dist.prepare_distribution_metadata(finder, build_isolation)
  File "/home/marco/sources/tests/more_itertools/venv/lib/python3.9/site-packages/pip/_internal/distributions/source/legacy.py", line 37, in prepare_distribution_metadata
    self._setup_isolation(finder)
  File "/home/marco/sources/tests/more_itertools/venv/lib/python3.9/site-packages/pip/_internal/distributions/source/legacy.py", line 90, in _setup_isolation
    reqs = backend.get_requires_for_build_wheel()
  File "/home/marco/sources/tests/more_itertools/venv/lib/python3.9/site-packages/pip/_vendor/pep517/wrappers.py", line 151, in get_requires_for_build_wheel
    return self._call_hook('get_requires_for_build_wheel', {
  File "/home/marco/sources/tests/more_itertools/venv/lib/python3.9/site-packages/pip/_vendor/pep517/wrappers.py", line 255, in _call_hook
    raise BackendUnavailable(data.get('traceback', ''))
pip._vendor.pep517.wrappers.BackendUnavailable: Traceback (most recent call last):
  File "/home/marco/sources/tests/more_itertools/venv/lib/python3.9/site-packages/pip/_vendor/pep517/_in_process.py", line 63, in _build_backend
    obj = import_module(mod_path)
  File "/usr/local/lib/python3.9/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1016, in _gcd_import
  File "<frozen importlib._bootstrap>", line 993, in _find_and_load
  File "<frozen importlib._bootstrap>", line 963, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 1016, in _gcd_import
  File "<frozen importlib._bootstrap>", line 993, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
ModuleNotFoundError: No module named 'setuptools'

所以我手动安装了依赖项并尝试 --no-deps:

(venv) marco@buzz:~/sources/tests/more_itertools/venv$ pip install numpy --no-deps
Collecting numpy
  Using cached https://files.pythonhosted.org/packages/31/0a/5df350c29a06835d534a6c4f5681075304da38d85f1c69e5226a635a67ce/numpy-1.18.0.zip
  Installing build dependencies ... error
[...]

和以前一样的错误。 --no-deps 被忽略，并且 --ignore-installed 强制从 Pypi 下载 Cython，这不适用于 Python 3.9.

显然，没有 --no-ignore-installed 或 --ignore-installed=0。以及

的事实

pip 忽略 --no-deps
如果在venv中注释掉--ignore-installed，pip找不到已经安装的模块

Answer 1

我在老 easy_install 上取得了成功，所以我认为现在还不错。我会报告这个错误（我猜是 venv 开发者）。

无法使用 Python 3.9 venv `pip install numpy`

Can't `pip install numpy` with a Python 3.9 venv

python

pip

python-venv

python-3.9

more-itertools