macOS Sierra opencv3安装 - 找不到“额外”模块

Question

我想在macOS Sierra上安装opencv-3.1.0。运行以下内容后：

This formula is keg-only, which means it was not symlinked into /usr/local.

opencv3 and opencv install many of the same files.

Generally there are no consequences of this for you. If you build your
own software and it requires this formula, you'll need to add to your
build variables:

    LDFLAGS:  -L/usr/local/opt/opencv3/lib
    CPPFLAGS: -I/usr/local/opt/opencv3/include
    PKG_CONFIG_PATH: /usr/local/opt/opencv3/lib/pkgconfig

它返回：

    sift = cv2.SIFT()
AttributeError: 'module' object has no attribute 'SIFT'

我可以从Python级别导入opencv，但看起来没有安装“额外”模块，特别是我需要SIFT

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任何想法如何解决？