再pycharm安装sklearn时出现Looking in indexes: https://pypi.tuna.tsinghua.edu.cn/simple Collecting sklearn Downloading https://pypi.tuna.tsinghua.edu.cn/packages/7a/93/e0e1b1e98f39dfca7ec9795cb46f6e09e88a2fd5d4a28e4b3d1f618a2aec/sklearn-0.0.post5.tar.gz (3.7 kB) Preparing metadata (setup.py): started Preparing metadata (setup.py): finished with status 'error' error: subprocess-exited-with-error python setup.py egg_info did not run successfully. exit code: 1 [18 lines of output] The 'sklearn' PyPI package is deprecated, use 'scikit-learn' rather than 'sklearn' for pip commands. Here is how to fix this error in the main use cases: - use 'pip install scikit-learn' rather than 'pip install sklearn' - replace 'sklearn' by 'scikit-learn' in your pip requirements files (requirements.txt, setup.py, setup.cfg, Pipfile, etc ...) - if the 'sklearn' package is used by one of your dependencies, it would be great if you take some time to track which package uses 'sklearn' instead of 'scikit-learn' and report it to their issue tracker - as a last resort, set the environment variable SKLEARN_ALLOW_DEPRECATED_SKLEARN_PACKAGE_INSTALL=True to avoid this error More information is available at https://github.com/scikit-learn/sklearn-pypi-package If the previous advice does not cover your use case, feel free to report it at https://github.com/scikit-learn/sklearn-pypi-package/issues/new [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. See above for output. note: This is an issue with the package mentioned above, not pip. hint: See above for details.是什么问题？该怎样解决？如何安装sklearn库？

这个错误是由于sklearn库已经被弃用，现在使用的是scikit-learn库，因此可以尝试使用以下命令安装scikit-learn库：

pip install -U scikit-learn

如果你仍然想安装旧版本的sklearn库，可以设置一个环境变量，以允许安装旧版本的sklearn：

SKLEARN_ALLOW_DEPRECATED_SKLEARN_PACKAGE_INSTALL=True

你可以在命令行中设置该环境变量，或者将其添加到你的操作系统环境变量中。