cmdclass 在 Python 的 setuptools 中做了什么？

Question

我最近收到了一个拉取请求，其中添加了

class build_ext(_build_ext):
    'to install numpy'
    def finalize_options(self):
        _build_ext.finalize_options(self)
        # Prevent numpy from thinking it is still in its setup process:
        __builtins__.__NUMPY_SETUP__ = False
        import numpy
        self.include_dirs.append(numpy.get_include())

到我的setup.py 导致：

from setuptools.command.build_ext import build_ext as _build_ext

try:
    from setuptools import setup
except ImportError:
    from distutils.core import setup


class build_ext(_build_ext):
    'to install numpy'
    def finalize_options(self):
        _build_ext.finalize_options(self)
        # Prevent numpy from thinking it is still in its setup process:
        __builtins__.__NUMPY_SETUP__ = False
        import numpy
        self.include_dirs.append(numpy.get_include())


config = {
    'cmdclass':{'build_ext':build_ext}, #numpy hack
    'setup_requires':['numpy'],         #numpy hack
    'name': 'nntoolkit',
    'version': '0.1.25',
    'author': 'Martin Thoma',
    'author_email': 'info@martin-thoma.de',
    'packages': ['nntoolkit'],
    'scripts': ['bin/nntoolkit'],
    'url': 'https://github.com/MartinThoma/nntoolkit',
    'license': 'MIT',
    'description': 'Neural Network Toolkit',
    'long_description': """...""",
    'install_requires': [
        "argparse",
        "theano",
        "nose",
        "natsort",
        "PyYAML",
        "matplotlib",
        "h5py",
        "numpy",
        "Cython"
    ],
    'keywords': ['Neural Networks', 'Feed-Forward', 'NN', 'MLP'],
    'download_url': 'https://github.com/MartinThoma/nntoolkit',
    'classifiers': ['Development Status :: 3 - Alpha'],
    'zip_safe': False,
    'test_suite': 'nose.collector'
}

setup(**config)

它有什么作用？

documentation 只声明：

cmdclass：命令名称到Command 子类的映射（字典）

Answer 1

Numpy 库是用 C/C++ 编写的。所以与其他包不同的是，它需要在实际调用它们之前进行编译。所以'build_ext'只是编译它们。

博客详情：http://sadafnoor.me/blog/how-to-automate-numpy-installation-in-your-project-using-setuptool/