OpenCV3.1 + Python2.7 error “DLL load failed: The specified module could not be found”

According to the web site [http://docs.opencv.org/3.1.0/d5/de5/tutorial_py_setup_in_windows.html] method 2 manual compiled OpenCV3.1.0 and install python.
but error “DLL load failed: The specified module could not be found” appears when importing cv2.
I looked for the following reasons online, the possible reason is that
1) opencv and python corresponding versions are different, such as one is 32bit and one is 64bit. Pyd
2) did not add cv2.pyd to C:/Python27/lib/site-packages
3) system environment variable could not be found cv2.pyd
the final solution to my computer problem was:
add [C:\ opencv-3.1.0 \build\bin\Release] to system environment variable.

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